2024-12-10 00:17:37 +03:00
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From de7a1729144df5a664b32643fc2246da8021e01c Mon Sep 17 00:00:00 2001
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2024-10-29 05:12:06 +03:00
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From: Neal Cardwell <ncardwell@google.com>
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Date: Tue, 11 Jun 2019 12:54:22 -0400
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Subject: [PATCH 16/19] net-tcp_bbr: v3: update TCP "bbr" congestion control
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module to BBRv3
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BBR v3 is an enhacement to the BBR v1 algorithm. It's designed to aim for lower
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queues, lower loss, and better Reno/CUBIC coexistence than BBR v1.
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BBR v3 maintains the core of BBR v1: an explicit model of the network
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path that is two-dimensional, adapting to estimate the (a) maximum
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available bandwidth and (b) maximum safe volume of data a flow can
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keep in-flight in the network. It maintains the estimated BDP as a
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core guide for estimating an appropriate level of in-flight data.
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BBR v3 makes several key enhancements:
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o Its bandwidth-probing time scale is adapted, within bounds, to allow improved
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coexistence with Reno and CUBIC. The bandwidth-probing time scale is (a)
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extended dynamically based on estimated BDP to improve coexistence with
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Reno/CUBIC; (b) bounded by an interactive wall-clock time-scale to be more
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scalable and responsive than Reno and CUBIC.
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o Rather than being largely agnostic to loss and ECN marks, it explicitly uses
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loss and (DCTCP-style) ECN signals to maintain its model.
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o It aims for lower losses than v1 by adjusting its model to attempt to stay
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within loss rate and ECN mark rate bounds (loss_thresh and ecn_thresh,
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respectively).
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o It adapts to loss/ECN signals even when the application is running out of
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data ("application-limited"), in case the "application-limited" flow is also
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"network-limited" (the bw and/or inflight available to this flow is lower than
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previously estimated when the flow ran out of data).
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o It has a three-part model: the model explicit three tracks operating points,
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where an operating point is a tuple: (bandwidth, inflight). The three operating
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points are:
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o latest: the latest measurement from the current round trip
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o upper bound: robust, optimistic, long-term upper bound
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o lower bound: robust, conservative, short-term lower bound
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These are stored in the following state variables:
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o latest: bw_latest, inflight_latest
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o lo: bw_lo, inflight_lo
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o hi: bw_hi[2], inflight_hi
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To gain intuition about the meaning of the three operating points, it
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may help to consider the analogs in CUBIC, which has a somewhat
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analogous three-part model used by its probing state machine:
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BBR param CUBIC param
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----------- -------------
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latest ~ cwnd
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lo ~ ssthresh
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hi ~ last_max_cwnd
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The analogy is only a loose one, though, since the BBR operating
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points are calculated differently, and are 2-dimensional (bw,inflight)
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rather than CUBIC's one-dimensional notion of operating point
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(inflight).
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o It uses the three-part model to adapt the magnitude of its bandwidth
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to match the estimated space available in the buffer, rather than (as
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in BBR v1) assuming that it was always acceptable to place 0.25*BDP in
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the bottleneck buffer when probing (commodity datacenter switches
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commonly do not have that much buffer for WAN flows). When BBR v3
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estimates it hit a buffer limit during probing, its bandwidth probing
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then starts gently in case little space is still available in the
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buffer, and the accelerates, slowly at first and then rapidly if it
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can grow inflight without seeing congestion signals. In such cases,
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probing is bounded by inflight_hi + inflight_probe, where
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inflight_probe grows as: [0, 1, 2, 4, 8, 16,...]. This allows BBR to
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keep losses low and bounded if a bottleneck remains congested, while
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rapidly/scalably utilizing free bandwidth when it becomes available.
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o It has a slightly revised state machine, to achieve the goals above.
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BBR_BW_PROBE_UP: pushes up inflight to probe for bw/vol
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BBR_BW_PROBE_DOWN: drain excess inflight from the queue
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BBR_BW_PROBE_CRUISE: use pipe, w/ headroom in queue/pipe
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BBR_BW_PROBE_REFILL: try refill the pipe again to 100%, leaving queue empty
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o The estimated BDP: BBR v3 continues to maintain an estimate of the
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path's two-way propagation delay, by tracking a windowed min_rtt, and
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coordinating (on an as-ndeeded basis) to try to expose the two-way
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propagation delay by draining the bottleneck queue.
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BBR v3 continues to use its min_rtt and (currently-applicable) bandwidth
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estimate to estimate the current bandwidth-delay product. The estimated BDP
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still provides one important guideline for bounding inflight data. However,
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because any min-filtered RTT and max-filtered bw inherently tend to both
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overestimate, the estimated BDP is often too high; in this case loss or ECN
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marks can ensue, in which case BBR v3 adjusts inflight_hi and inflight_lo to
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adapt its sending rate and inflight down to match the available capacity of the
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path.
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o Space: Note that ICSK_CA_PRIV_SIZE increased. This is because BBR v3
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requires more space. Note that much of the space is due to support for
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per-socket parameterization and debugging in this release for research
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and debugging. With that state removed, the full "struct bbr" is 140
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bytes, or 144 with padding. This is an increase of 40 bytes over the
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existing ca_priv space.
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o Code: BBR v3 reuses many pieces from BBR v1. But it omits the following
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significant pieces:
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o "packet conservation" (bbr_set_cwnd_to_recover_or_restore(),
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bbr_can_grow_inflight())
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o long-term bandwidth estimator ("policer mode")
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The code layout tries to keep BBR v3 code near the bottom of the
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file, so that v1-applicable code in the top does not accidentally
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refer to v3 code.
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o Docs:
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See the following docs for more details and diagrams decsribing the BBR v3
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algorithm:
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https://datatracker.ietf.org/meeting/104/materials/slides-104-iccrg-an-update-on-bbr-00
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https://datatracker.ietf.org/meeting/102/materials/slides-102-iccrg-an-update-on-bbr-work-at-google-00
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o Internal notes:
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For this upstream rebase, Neal started from:
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git show fed518041ac6:net/ipv4/tcp_bbr.c > net/ipv4/tcp_bbr.c
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then removed dev instrumentation (dynamic get/set for parameters)
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and code that was only used by BBRv1
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Effort: net-tcp_bbr
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Origin-9xx-SHA1: 2c84098e60bed6d67dde23cd7538c51dee273102
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Change-Id: I125cf26ba2a7a686f2fa5e87f4c2afceb65f7a05
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Signed-off-by: Alexandre Frade <kernel@xanmod.org>
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---
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include/net/inet_connection_sock.h | 4 +-
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include/net/tcp.h | 2 +-
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include/uapi/linux/inet_diag.h | 23 +
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net/ipv4/Kconfig | 21 +-
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net/ipv4/tcp_bbr.c | 2214 +++++++++++++++++++++-------
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5 files changed, 1740 insertions(+), 524 deletions(-)
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--- a/include/net/inet_connection_sock.h
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+++ b/include/net/inet_connection_sock.h
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@@ -137,8 +137,8 @@ struct inet_connection_sock {
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u32 icsk_probes_tstamp;
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u32 icsk_user_timeout;
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- u64 icsk_ca_priv[104 / sizeof(u64)];
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-#define ICSK_CA_PRIV_SIZE sizeof_field(struct inet_connection_sock, icsk_ca_priv)
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+#define ICSK_CA_PRIV_SIZE (144)
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+ u64 icsk_ca_priv[ICSK_CA_PRIV_SIZE / sizeof(u64)];
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};
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#define ICSK_TIME_RETRANS 1 /* Retransmit timer */
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--- a/include/net/tcp.h
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+++ b/include/net/tcp.h
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2024-12-10 00:17:37 +03:00
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@@ -2474,7 +2474,7 @@ struct tcp_plb_state {
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2024-10-29 05:12:06 +03:00
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u8 consec_cong_rounds:5, /* consecutive congested rounds */
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unused:3;
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u32 pause_until; /* jiffies32 when PLB can resume rerouting */
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-};
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+} __attribute__ ((__packed__));
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static inline void tcp_plb_init(const struct sock *sk,
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struct tcp_plb_state *plb)
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--- a/include/uapi/linux/inet_diag.h
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+++ b/include/uapi/linux/inet_diag.h
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@@ -229,6 +229,29 @@ struct tcp_bbr_info {
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__u32 bbr_min_rtt; /* min-filtered RTT in uSec */
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__u32 bbr_pacing_gain; /* pacing gain shifted left 8 bits */
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__u32 bbr_cwnd_gain; /* cwnd gain shifted left 8 bits */
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+ __u32 bbr_bw_hi_lsb; /* lower 32 bits of bw_hi */
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+ __u32 bbr_bw_hi_msb; /* upper 32 bits of bw_hi */
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+ __u32 bbr_bw_lo_lsb; /* lower 32 bits of bw_lo */
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+ __u32 bbr_bw_lo_msb; /* upper 32 bits of bw_lo */
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+ __u8 bbr_mode; /* current bbr_mode in state machine */
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+ __u8 bbr_phase; /* current state machine phase */
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+ __u8 unused1; /* alignment padding; not used yet */
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+ __u8 bbr_version; /* BBR algorithm version */
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+ __u32 bbr_inflight_lo; /* lower short-term data volume bound */
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+ __u32 bbr_inflight_hi; /* higher long-term data volume bound */
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+ __u32 bbr_extra_acked; /* max excess packets ACKed in epoch */
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+};
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+
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+/* TCP BBR congestion control bbr_phase as reported in netlink/ss stats. */
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+enum tcp_bbr_phase {
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+ BBR_PHASE_INVALID = 0,
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+ BBR_PHASE_STARTUP = 1,
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+ BBR_PHASE_DRAIN = 2,
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+ BBR_PHASE_PROBE_RTT = 3,
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+ BBR_PHASE_PROBE_BW_UP = 4,
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+ BBR_PHASE_PROBE_BW_DOWN = 5,
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+ BBR_PHASE_PROBE_BW_CRUISE = 6,
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+ BBR_PHASE_PROBE_BW_REFILL = 7,
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};
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union tcp_cc_info {
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--- a/net/ipv4/Kconfig
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+++ b/net/ipv4/Kconfig
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2024-12-10 00:17:37 +03:00
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@@ -669,15 +669,18 @@ config TCP_CONG_BBR
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2024-10-29 05:12:06 +03:00
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default n
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help
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- BBR (Bottleneck Bandwidth and RTT) TCP congestion control aims to
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- maximize network utilization and minimize queues. It builds an explicit
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- model of the bottleneck delivery rate and path round-trip propagation
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- delay. It tolerates packet loss and delay unrelated to congestion. It
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- can operate over LAN, WAN, cellular, wifi, or cable modem links. It can
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- coexist with flows that use loss-based congestion control, and can
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- operate with shallow buffers, deep buffers, bufferbloat, policers, or
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- AQM schemes that do not provide a delay signal. It requires the fq
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- ("Fair Queue") pacing packet scheduler.
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+ BBR (Bottleneck Bandwidth and RTT) TCP congestion control is a
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+ model-based congestion control algorithm that aims to maximize
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+ network utilization, keep queues and retransmit rates low, and to be
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+ able to coexist with Reno/CUBIC in common scenarios. It builds an
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+ explicit model of the network path. It tolerates a targeted degree
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+ of random packet loss and delay. It can operate over LAN, WAN,
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+ cellular, wifi, or cable modem links, and can use shallow-threshold
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+ ECN signals. It can coexist to some degree with flows that use
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+ loss-based congestion control, and can operate with shallow buffers,
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+ deep buffers, bufferbloat, policers, or AQM schemes that do not
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+ provide a delay signal. It requires pacing, using either TCP internal
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+ pacing or the fq ("Fair Queue") pacing packet scheduler.
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choice
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prompt "Default TCP congestion control"
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--- a/net/ipv4/tcp_bbr.c
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+++ b/net/ipv4/tcp_bbr.c
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@@ -1,18 +1,19 @@
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-/* Bottleneck Bandwidth and RTT (BBR) congestion control
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+/* BBR (Bottleneck Bandwidth and RTT) congestion control
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*
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- * BBR congestion control computes the sending rate based on the delivery
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- * rate (throughput) estimated from ACKs. In a nutshell:
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+ * BBR is a model-based congestion control algorithm that aims for low queues,
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+ * low loss, and (bounded) Reno/CUBIC coexistence. To maintain a model of the
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+ * network path, it uses measurements of bandwidth and RTT, as well as (if they
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+ * occur) packet loss and/or shallow-threshold ECN signals. Note that although
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+ * it can use ECN or loss signals explicitly, it does not require either; it
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+ * can bound its in-flight data based on its estimate of the BDP.
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*
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- * On each ACK, update our model of the network path:
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- * bottleneck_bandwidth = windowed_max(delivered / elapsed, 10 round trips)
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- * min_rtt = windowed_min(rtt, 10 seconds)
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- * pacing_rate = pacing_gain * bottleneck_bandwidth
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- * cwnd = max(cwnd_gain * bottleneck_bandwidth * min_rtt, 4)
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- *
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- * The core algorithm does not react directly to packet losses or delays,
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- * although BBR may adjust the size of next send per ACK when loss is
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- * observed, or adjust the sending rate if it estimates there is a
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- * traffic policer, in order to keep the drop rate reasonable.
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+ * The model has both higher and lower bounds for the operating range:
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+ * lo: bw_lo, inflight_lo: conservative short-term lower bound
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+ * hi: bw_hi, inflight_hi: robust long-term upper bound
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+ * The bandwidth-probing time scale is (a) extended dynamically based on
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+ * estimated BDP to improve coexistence with Reno/CUBIC; (b) bounded by
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+ * an interactive wall-clock time-scale to be more scalable and responsive
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+ * than Reno and CUBIC.
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*
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* Here is a state transition diagram for BBR:
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*
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@@ -65,6 +66,13 @@
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#include <linux/random.h>
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#include <linux/win_minmax.h>
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+#include <trace/events/tcp.h>
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+#include "tcp_dctcp.h"
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+
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+#define BBR_VERSION 3
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+
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+#define bbr_param(sk,name) (bbr_ ## name)
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+
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/* Scale factor for rate in pkt/uSec unit to avoid truncation in bandwidth
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* estimation. The rate unit ~= (1500 bytes / 1 usec / 2^24) ~= 715 bps.
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* This handles bandwidths from 0.06pps (715bps) to 256Mpps (3Tbps) in a u32.
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@@ -85,36 +93,41 @@ enum bbr_mode {
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BBR_PROBE_RTT, /* cut inflight to min to probe min_rtt */
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};
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+/* How does the incoming ACK stream relate to our bandwidth probing? */
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+enum bbr_ack_phase {
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+ BBR_ACKS_INIT, /* not probing; not getting probe feedback */
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+ BBR_ACKS_REFILLING, /* sending at est. bw to fill pipe */
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+ BBR_ACKS_PROBE_STARTING, /* inflight rising to probe bw */
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+ BBR_ACKS_PROBE_FEEDBACK, /* getting feedback from bw probing */
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+ BBR_ACKS_PROBE_STOPPING, /* stopped probing; still getting feedback */
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+};
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+
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/* BBR congestion control block */
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struct bbr {
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u32 min_rtt_us; /* min RTT in min_rtt_win_sec window */
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u32 min_rtt_stamp; /* timestamp of min_rtt_us */
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u32 probe_rtt_done_stamp; /* end time for BBR_PROBE_RTT mode */
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- struct minmax bw; /* Max recent delivery rate in pkts/uS << 24 */
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- u32 rtt_cnt; /* count of packet-timed rounds elapsed */
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+ u32 probe_rtt_min_us; /* min RTT in probe_rtt_win_ms win */
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+ u32 probe_rtt_min_stamp; /* timestamp of probe_rtt_min_us*/
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u32 next_rtt_delivered; /* scb->tx.delivered at end of round */
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u64 cycle_mstamp; /* time of this cycle phase start */
|
|
|
|
- u32 mode:3, /* current bbr_mode in state machine */
|
|
|
|
+ u32 mode:2, /* current bbr_mode in state machine */
|
|
|
|
prev_ca_state:3, /* CA state on previous ACK */
|
|
|
|
- packet_conservation:1, /* use packet conservation? */
|
|
|
|
round_start:1, /* start of packet-timed tx->ack round? */
|
|
|
|
+ ce_state:1, /* If most recent data has CE bit set */
|
|
|
|
+ bw_probe_up_rounds:5, /* cwnd-limited rounds in PROBE_UP */
|
|
|
|
+ try_fast_path:1, /* can we take fast path? */
|
|
|
|
idle_restart:1, /* restarting after idle? */
|
|
|
|
probe_rtt_round_done:1, /* a BBR_PROBE_RTT round at 4 pkts? */
|
|
|
|
- unused:13,
|
|
|
|
- lt_is_sampling:1, /* taking long-term ("LT") samples now? */
|
|
|
|
- lt_rtt_cnt:7, /* round trips in long-term interval */
|
|
|
|
- lt_use_bw:1; /* use lt_bw as our bw estimate? */
|
|
|
|
- u32 lt_bw; /* LT est delivery rate in pkts/uS << 24 */
|
|
|
|
- u32 lt_last_delivered; /* LT intvl start: tp->delivered */
|
|
|
|
- u32 lt_last_stamp; /* LT intvl start: tp->delivered_mstamp */
|
|
|
|
- u32 lt_last_lost; /* LT intvl start: tp->lost */
|
|
|
|
+ init_cwnd:7, /* initial cwnd */
|
|
|
|
+ unused_1:10;
|
|
|
|
u32 pacing_gain:10, /* current gain for setting pacing rate */
|
|
|
|
cwnd_gain:10, /* current gain for setting cwnd */
|
|
|
|
full_bw_reached:1, /* reached full bw in Startup? */
|
|
|
|
full_bw_cnt:2, /* number of rounds without large bw gains */
|
|
|
|
- cycle_idx:3, /* current index in pacing_gain cycle array */
|
|
|
|
+ cycle_idx:2, /* current index in pacing_gain cycle array */
|
|
|
|
has_seen_rtt:1, /* have we seen an RTT sample yet? */
|
|
|
|
- unused_b:5;
|
|
|
|
+ unused_2:6;
|
|
|
|
u32 prior_cwnd; /* prior cwnd upon entering loss recovery */
|
|
|
|
u32 full_bw; /* recent bw, to estimate if pipe is full */
|
|
|
|
|
|
|
|
@@ -124,19 +137,67 @@ struct bbr {
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|
|
u32 ack_epoch_acked:20, /* packets (S)ACKed in sampling epoch */
|
|
|
|
extra_acked_win_rtts:5, /* age of extra_acked, in round trips */
|
|
|
|
extra_acked_win_idx:1, /* current index in extra_acked array */
|
|
|
|
- unused_c:6;
|
|
|
|
+ /* BBR v3 state: */
|
|
|
|
+ full_bw_now:1, /* recently reached full bw plateau? */
|
|
|
|
+ startup_ecn_rounds:2, /* consecutive hi ECN STARTUP rounds */
|
|
|
|
+ loss_in_cycle:1, /* packet loss in this cycle? */
|
|
|
|
+ ecn_in_cycle:1, /* ECN in this cycle? */
|
|
|
|
+ unused_3:1;
|
|
|
|
+ u32 loss_round_delivered; /* scb->tx.delivered ending loss round */
|
|
|
|
+ u32 undo_bw_lo; /* bw_lo before latest losses */
|
|
|
|
+ u32 undo_inflight_lo; /* inflight_lo before latest losses */
|
|
|
|
+ u32 undo_inflight_hi; /* inflight_hi before latest losses */
|
|
|
|
+ u32 bw_latest; /* max delivered bw in last round trip */
|
|
|
|
+ u32 bw_lo; /* lower bound on sending bandwidth */
|
|
|
|
+ u32 bw_hi[2]; /* max recent measured bw sample */
|
|
|
|
+ u32 inflight_latest; /* max delivered data in last round trip */
|
|
|
|
+ u32 inflight_lo; /* lower bound of inflight data range */
|
|
|
|
+ u32 inflight_hi; /* upper bound of inflight data range */
|
|
|
|
+ u32 bw_probe_up_cnt; /* packets delivered per inflight_hi incr */
|
|
|
|
+ u32 bw_probe_up_acks; /* packets (S)ACKed since inflight_hi incr */
|
|
|
|
+ u32 probe_wait_us; /* PROBE_DOWN until next clock-driven probe */
|
|
|
|
+ u32 prior_rcv_nxt; /* tp->rcv_nxt when CE state last changed */
|
|
|
|
+ u32 ecn_eligible:1, /* sender can use ECN (RTT, handshake)? */
|
|
|
|
+ ecn_alpha:9, /* EWMA delivered_ce/delivered; 0..256 */
|
|
|
|
+ bw_probe_samples:1, /* rate samples reflect bw probing? */
|
|
|
|
+ prev_probe_too_high:1, /* did last PROBE_UP go too high? */
|
|
|
|
+ stopped_risky_probe:1, /* last PROBE_UP stopped due to risk? */
|
|
|
|
+ rounds_since_probe:8, /* packet-timed rounds since probed bw */
|
|
|
|
+ loss_round_start:1, /* loss_round_delivered round trip? */
|
|
|
|
+ loss_in_round:1, /* loss marked in this round trip? */
|
|
|
|
+ ecn_in_round:1, /* ECN marked in this round trip? */
|
|
|
|
+ ack_phase:3, /* bbr_ack_phase: meaning of ACKs */
|
|
|
|
+ loss_events_in_round:4,/* losses in STARTUP round */
|
|
|
|
+ initialized:1; /* has bbr_init() been called? */
|
|
|
|
+ u32 alpha_last_delivered; /* tp->delivered at alpha update */
|
|
|
|
+ u32 alpha_last_delivered_ce; /* tp->delivered_ce at alpha update */
|
|
|
|
+
|
|
|
|
+ u8 unused_4; /* to preserve alignment */
|
|
|
|
+ struct tcp_plb_state plb;
|
|
|
|
};
|
|
|
|
|
|
|
|
-#define CYCLE_LEN 8 /* number of phases in a pacing gain cycle */
|
|
|
|
+struct bbr_context {
|
|
|
|
+ u32 sample_bw;
|
|
|
|
+};
|
|
|
|
|
|
|
|
-/* Window length of bw filter (in rounds): */
|
|
|
|
-static const int bbr_bw_rtts = CYCLE_LEN + 2;
|
|
|
|
/* Window length of min_rtt filter (in sec): */
|
|
|
|
static const u32 bbr_min_rtt_win_sec = 10;
|
|
|
|
/* Minimum time (in ms) spent at bbr_cwnd_min_target in BBR_PROBE_RTT mode: */
|
|
|
|
static const u32 bbr_probe_rtt_mode_ms = 200;
|
|
|
|
-/* Skip TSO below the following bandwidth (bits/sec): */
|
|
|
|
-static const int bbr_min_tso_rate = 1200000;
|
|
|
|
+/* Window length of probe_rtt_min_us filter (in ms), and consequently the
|
|
|
|
+ * typical interval between PROBE_RTT mode entries. The default is 5000ms.
|
|
|
|
+ * Note that bbr_probe_rtt_win_ms must be <= bbr_min_rtt_win_sec * MSEC_PER_SEC
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_probe_rtt_win_ms = 5000;
|
|
|
|
+/* Proportion of cwnd to estimated BDP in PROBE_RTT, in units of BBR_UNIT: */
|
|
|
|
+static const u32 bbr_probe_rtt_cwnd_gain = BBR_UNIT * 1 / 2;
|
|
|
|
+
|
|
|
|
+/* Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting
|
|
|
|
+ * in bigger TSO bursts. We cut the RTT-based allowance in half
|
|
|
|
+ * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance
|
|
|
|
+ * is below 1500 bytes after 6 * ~500 usec = 3ms.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_tso_rtt_shift = 9;
|
|
|
|
|
|
|
|
/* Pace at ~1% below estimated bw, on average, to reduce queue at bottleneck.
|
|
|
|
* In order to help drive the network toward lower queues and low latency while
|
|
|
|
@@ -146,13 +207,15 @@ static const int bbr_min_tso_rate = 1200
|
|
|
|
*/
|
|
|
|
static const int bbr_pacing_margin_percent = 1;
|
|
|
|
|
|
|
|
-/* We use a high_gain value of 2/ln(2) because it's the smallest pacing gain
|
|
|
|
+/* We use a startup_pacing_gain of 4*ln(2) because it's the smallest value
|
|
|
|
* that will allow a smoothly increasing pacing rate that will double each RTT
|
|
|
|
* and send the same number of packets per RTT that an un-paced, slow-starting
|
|
|
|
* Reno or CUBIC flow would:
|
|
|
|
*/
|
|
|
|
-static const int bbr_high_gain = BBR_UNIT * 2885 / 1000 + 1;
|
|
|
|
-/* The pacing gain of 1/high_gain in BBR_DRAIN is calculated to typically drain
|
|
|
|
+static const int bbr_startup_pacing_gain = BBR_UNIT * 277 / 100 + 1;
|
|
|
|
+/* The gain for deriving startup cwnd: */
|
|
|
|
+static const int bbr_startup_cwnd_gain = BBR_UNIT * 2;
|
|
|
|
+/* The pacing gain in BBR_DRAIN is calculated to typically drain
|
|
|
|
* the queue created in BBR_STARTUP in a single round:
|
|
|
|
*/
|
|
|
|
static const int bbr_drain_gain = BBR_UNIT * 1000 / 2885;
|
|
|
|
@@ -160,13 +223,17 @@ static const int bbr_drain_gain = BBR_UN
|
|
|
|
static const int bbr_cwnd_gain = BBR_UNIT * 2;
|
|
|
|
/* The pacing_gain values for the PROBE_BW gain cycle, to discover/share bw: */
|
|
|
|
static const int bbr_pacing_gain[] = {
|
|
|
|
- BBR_UNIT * 5 / 4, /* probe for more available bw */
|
|
|
|
- BBR_UNIT * 3 / 4, /* drain queue and/or yield bw to other flows */
|
|
|
|
- BBR_UNIT, BBR_UNIT, BBR_UNIT, /* cruise at 1.0*bw to utilize pipe, */
|
|
|
|
- BBR_UNIT, BBR_UNIT, BBR_UNIT /* without creating excess queue... */
|
|
|
|
+ BBR_UNIT * 5 / 4, /* UP: probe for more available bw */
|
|
|
|
+ BBR_UNIT * 91 / 100, /* DOWN: drain queue and/or yield bw */
|
|
|
|
+ BBR_UNIT, /* CRUISE: try to use pipe w/ some headroom */
|
|
|
|
+ BBR_UNIT, /* REFILL: refill pipe to estimated 100% */
|
|
|
|
+};
|
|
|
|
+enum bbr_pacing_gain_phase {
|
|
|
|
+ BBR_BW_PROBE_UP = 0, /* push up inflight to probe for bw/vol */
|
|
|
|
+ BBR_BW_PROBE_DOWN = 1, /* drain excess inflight from the queue */
|
|
|
|
+ BBR_BW_PROBE_CRUISE = 2, /* use pipe, w/ headroom in queue/pipe */
|
|
|
|
+ BBR_BW_PROBE_REFILL = 3, /* v2: refill the pipe again to 100% */
|
|
|
|
};
|
|
|
|
-/* Randomize the starting gain cycling phase over N phases: */
|
|
|
|
-static const u32 bbr_cycle_rand = 7;
|
|
|
|
|
|
|
|
/* Try to keep at least this many packets in flight, if things go smoothly. For
|
|
|
|
* smooth functioning, a sliding window protocol ACKing every other packet
|
|
|
|
@@ -174,24 +241,12 @@ static const u32 bbr_cycle_rand = 7;
|
|
|
|
*/
|
|
|
|
static const u32 bbr_cwnd_min_target = 4;
|
|
|
|
|
|
|
|
-/* To estimate if BBR_STARTUP mode (i.e. high_gain) has filled pipe... */
|
|
|
|
+/* To estimate if BBR_STARTUP or BBR_BW_PROBE_UP has filled pipe... */
|
|
|
|
/* If bw has increased significantly (1.25x), there may be more bw available: */
|
|
|
|
static const u32 bbr_full_bw_thresh = BBR_UNIT * 5 / 4;
|
|
|
|
/* But after 3 rounds w/o significant bw growth, estimate pipe is full: */
|
|
|
|
static const u32 bbr_full_bw_cnt = 3;
|
|
|
|
|
|
|
|
-/* "long-term" ("LT") bandwidth estimator parameters... */
|
|
|
|
-/* The minimum number of rounds in an LT bw sampling interval: */
|
|
|
|
-static const u32 bbr_lt_intvl_min_rtts = 4;
|
|
|
|
-/* If lost/delivered ratio > 20%, interval is "lossy" and we may be policed: */
|
|
|
|
-static const u32 bbr_lt_loss_thresh = 50;
|
|
|
|
-/* If 2 intervals have a bw ratio <= 1/8, their bw is "consistent": */
|
|
|
|
-static const u32 bbr_lt_bw_ratio = BBR_UNIT / 8;
|
|
|
|
-/* If 2 intervals have a bw diff <= 4 Kbit/sec their bw is "consistent": */
|
|
|
|
-static const u32 bbr_lt_bw_diff = 4000 / 8;
|
|
|
|
-/* If we estimate we're policed, use lt_bw for this many round trips: */
|
|
|
|
-static const u32 bbr_lt_bw_max_rtts = 48;
|
|
|
|
-
|
|
|
|
/* Gain factor for adding extra_acked to target cwnd: */
|
|
|
|
static const int bbr_extra_acked_gain = BBR_UNIT;
|
|
|
|
/* Window length of extra_acked window. */
|
|
|
|
@@ -201,8 +256,121 @@ static const u32 bbr_ack_epoch_acked_res
|
|
|
|
/* Time period for clamping cwnd increment due to ack aggregation */
|
|
|
|
static const u32 bbr_extra_acked_max_us = 100 * 1000;
|
|
|
|
|
|
|
|
+/* Flags to control BBR ECN-related behavior... */
|
|
|
|
+
|
|
|
|
+/* Ensure ACKs only ACK packets with consistent ECN CE status? */
|
|
|
|
+static const bool bbr_precise_ece_ack = true;
|
|
|
|
+
|
|
|
|
+/* Max RTT (in usec) at which to use sender-side ECN logic.
|
|
|
|
+ * Disabled when 0 (ECN allowed at any RTT).
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_ecn_max_rtt_us = 5000;
|
|
|
|
+
|
|
|
|
+/* On losses, scale down inflight and pacing rate by beta scaled by BBR_SCALE.
|
|
|
|
+ * No loss response when 0.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_beta = BBR_UNIT * 30 / 100;
|
|
|
|
+
|
|
|
|
+/* Gain factor for ECN mark ratio samples, scaled by BBR_SCALE (1/16 = 6.25%) */
|
|
|
|
+static const u32 bbr_ecn_alpha_gain = BBR_UNIT * 1 / 16;
|
|
|
|
+
|
|
|
|
+/* The initial value for ecn_alpha; 1.0 allows a flow to respond quickly
|
|
|
|
+ * to congestion if the bottleneck is congested when the flow starts up.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_ecn_alpha_init = BBR_UNIT;
|
|
|
|
+
|
|
|
|
+/* On ECN, cut inflight_lo to (1 - ecn_factor * ecn_alpha) scaled by BBR_SCALE.
|
|
|
|
+ * No ECN based bounding when 0.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_ecn_factor = BBR_UNIT * 1 / 3; /* 1/3 = 33% */
|
|
|
|
+
|
|
|
|
+/* Estimate bw probing has gone too far if CE ratio exceeds this threshold.
|
|
|
|
+ * Scaled by BBR_SCALE. Disabled when 0.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_ecn_thresh = BBR_UNIT * 1 / 2; /* 1/2 = 50% */
|
|
|
|
+
|
|
|
|
+/* If non-zero, if in a cycle with no losses but some ECN marks, after ECN
|
|
|
|
+ * clears then make the first round's increment to inflight_hi the following
|
|
|
|
+ * fraction of inflight_hi.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_ecn_reprobe_gain = BBR_UNIT * 1 / 2;
|
|
|
|
+
|
|
|
|
+/* Estimate bw probing has gone too far if loss rate exceeds this level. */
|
|
|
|
+static const u32 bbr_loss_thresh = BBR_UNIT * 2 / 100; /* 2% loss */
|
|
|
|
+
|
|
|
|
+/* Slow down for a packet loss recovered by TLP? */
|
|
|
|
+static const bool bbr_loss_probe_recovery = true;
|
|
|
|
+
|
|
|
|
+/* Exit STARTUP if number of loss marking events in a Recovery round is >= N,
|
|
|
|
+ * and loss rate is higher than bbr_loss_thresh.
|
|
|
|
+ * Disabled if 0.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_full_loss_cnt = 6;
|
|
|
|
+
|
|
|
|
+/* Exit STARTUP if number of round trips with ECN mark rate above ecn_thresh
|
|
|
|
+ * meets this count.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_full_ecn_cnt = 2;
|
|
|
|
+
|
|
|
|
+/* Fraction of unutilized headroom to try to leave in path upon high loss. */
|
|
|
|
+static const u32 bbr_inflight_headroom = BBR_UNIT * 15 / 100;
|
|
|
|
+
|
|
|
|
+/* How much do we increase cwnd_gain when probing for bandwidth in
|
|
|
|
+ * BBR_BW_PROBE_UP? This specifies the increment in units of
|
|
|
|
+ * BBR_UNIT/4. The default is 1, meaning 0.25.
|
|
|
|
+ * The min value is 0 (meaning 0.0); max is 3 (meaning 0.75).
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_bw_probe_cwnd_gain = 1;
|
|
|
|
+
|
|
|
|
+/* Max number of packet-timed rounds to wait before probing for bandwidth. If
|
|
|
|
+ * we want to tolerate 1% random loss per round, and not have this cut our
|
|
|
|
+ * inflight too much, we must probe for bw periodically on roughly this scale.
|
|
|
|
+ * If low, limits Reno/CUBIC coexistence; if high, limits loss tolerance.
|
|
|
|
+ * We aim to be fair with Reno/CUBIC up to a BDP of at least:
|
|
|
|
+ * BDP = 25Mbps * .030sec /(1514bytes) = 61.9 packets
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_bw_probe_max_rounds = 63;
|
|
|
|
+
|
|
|
|
+/* Max amount of randomness to inject in round counting for Reno-coexistence.
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_bw_probe_rand_rounds = 2;
|
|
|
|
+
|
|
|
|
+/* Use BBR-native probe time scale starting at this many usec.
|
|
|
|
+ * We aim to be fair with Reno/CUBIC up to an inter-loss time epoch of at least:
|
|
|
|
+ * BDP*RTT = 25Mbps * .030sec /(1514bytes) * 0.030sec = 1.9 secs
|
|
|
|
+ */
|
|
|
|
+static const u32 bbr_bw_probe_base_us = 2 * USEC_PER_SEC; /* 2 secs */
|
|
|
|
+
|
|
|
|
+/* Use BBR-native probes spread over this many usec: */
|
|
|
|
+static const u32 bbr_bw_probe_rand_us = 1 * USEC_PER_SEC; /* 1 secs */
|
|
|
|
+
|
|
|
|
+/* Use fast path if app-limited, no loss/ECN, and target cwnd was reached? */
|
|
|
|
+static const bool bbr_fast_path = true;
|
|
|
|
+
|
|
|
|
+/* Use fast ack mode? */
|
|
|
|
+static const bool bbr_fast_ack_mode = true;
|
|
|
|
+
|
|
|
|
+static u32 bbr_max_bw(const struct sock *sk);
|
|
|
|
+static u32 bbr_bw(const struct sock *sk);
|
|
|
|
+static void bbr_exit_probe_rtt(struct sock *sk);
|
|
|
|
+static void bbr_reset_congestion_signals(struct sock *sk);
|
|
|
|
+static void bbr_run_loss_probe_recovery(struct sock *sk);
|
|
|
|
+
|
|
|
|
static void bbr_check_probe_rtt_done(struct sock *sk);
|
|
|
|
|
|
|
|
+/* This connection can use ECN if both endpoints have signaled ECN support in
|
|
|
|
+ * the handshake and the per-route settings indicated this is a
|
|
|
|
+ * shallow-threshold ECN environment, meaning both:
|
|
|
|
+ * (a) ECN CE marks indicate low-latency/shallow-threshold congestion, and
|
|
|
|
+ * (b) TCP endpoints provide precise ACKs that only ACK data segments
|
|
|
|
+ * with consistent ECN CE status
|
|
|
|
+ */
|
|
|
|
+static bool bbr_can_use_ecn(const struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ return (tcp_sk(sk)->ecn_flags & TCP_ECN_OK) &&
|
|
|
|
+ (tcp_sk(sk)->ecn_flags & TCP_ECN_LOW);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
/* Do we estimate that STARTUP filled the pipe? */
|
|
|
|
static bool bbr_full_bw_reached(const struct sock *sk)
|
|
|
|
{
|
|
|
|
@@ -214,17 +382,17 @@ static bool bbr_full_bw_reached(const st
|
|
|
|
/* Return the windowed max recent bandwidth sample, in pkts/uS << BW_SCALE. */
|
|
|
|
static u32 bbr_max_bw(const struct sock *sk)
|
|
|
|
{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ const struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
|
|
|
|
- return minmax_get(&bbr->bw);
|
|
|
|
+ return max(bbr->bw_hi[0], bbr->bw_hi[1]);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Return the estimated bandwidth of the path, in pkts/uS << BW_SCALE. */
|
|
|
|
static u32 bbr_bw(const struct sock *sk)
|
|
|
|
{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ const struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
|
|
|
|
- return bbr->lt_use_bw ? bbr->lt_bw : bbr_max_bw(sk);
|
|
|
|
+ return min(bbr_max_bw(sk), bbr->bw_lo);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Return maximum extra acked in past k-2k round trips,
|
|
|
|
@@ -241,15 +409,23 @@ static u16 bbr_extra_acked(const struct
|
|
|
|
* The order here is chosen carefully to avoid overflow of u64. This should
|
|
|
|
* work for input rates of up to 2.9Tbit/sec and gain of 2.89x.
|
|
|
|
*/
|
|
|
|
-static u64 bbr_rate_bytes_per_sec(struct sock *sk, u64 rate, int gain)
|
|
|
|
+static u64 bbr_rate_bytes_per_sec(struct sock *sk, u64 rate, int gain,
|
|
|
|
+ int margin)
|
|
|
|
{
|
|
|
|
unsigned int mss = tcp_sk(sk)->mss_cache;
|
|
|
|
|
|
|
|
rate *= mss;
|
|
|
|
rate *= gain;
|
|
|
|
rate >>= BBR_SCALE;
|
|
|
|
- rate *= USEC_PER_SEC / 100 * (100 - bbr_pacing_margin_percent);
|
|
|
|
- return rate >> BW_SCALE;
|
|
|
|
+ rate *= USEC_PER_SEC / 100 * (100 - margin);
|
|
|
|
+ rate >>= BW_SCALE;
|
|
|
|
+ rate = max(rate, 1ULL);
|
|
|
|
+ return rate;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static u64 bbr_bw_bytes_per_sec(struct sock *sk, u64 rate)
|
|
|
|
+{
|
|
|
|
+ return bbr_rate_bytes_per_sec(sk, rate, BBR_UNIT, 0);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Convert a BBR bw and gain factor to a pacing rate in bytes per second. */
|
|
|
|
@@ -257,12 +433,13 @@ static unsigned long bbr_bw_to_pacing_ra
|
|
|
|
{
|
|
|
|
u64 rate = bw;
|
|
|
|
|
|
|
|
- rate = bbr_rate_bytes_per_sec(sk, rate, gain);
|
|
|
|
+ rate = bbr_rate_bytes_per_sec(sk, rate, gain,
|
|
|
|
+ bbr_pacing_margin_percent);
|
|
|
|
rate = min_t(u64, rate, READ_ONCE(sk->sk_max_pacing_rate));
|
|
|
|
return rate;
|
|
|
|
}
|
|
|
|
|
|
|
|
-/* Initialize pacing rate to: high_gain * init_cwnd / RTT. */
|
|
|
|
+/* Initialize pacing rate to: startup_pacing_gain * init_cwnd / RTT. */
|
|
|
|
static void bbr_init_pacing_rate_from_rtt(struct sock *sk)
|
|
|
|
{
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
@@ -279,7 +456,7 @@ static void bbr_init_pacing_rate_from_rt
|
|
|
|
bw = (u64)tcp_snd_cwnd(tp) * BW_UNIT;
|
|
|
|
do_div(bw, rtt_us);
|
|
|
|
WRITE_ONCE(sk->sk_pacing_rate,
|
|
|
|
- bbr_bw_to_pacing_rate(sk, bw, bbr_high_gain));
|
|
|
|
+ bbr_bw_to_pacing_rate(sk, bw, bbr_param(sk, startup_pacing_gain)));
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Pace using current bw estimate and a gain factor. */
|
|
|
|
@@ -295,31 +472,38 @@ static void bbr_set_pacing_rate(struct s
|
|
|
|
WRITE_ONCE(sk->sk_pacing_rate, rate);
|
|
|
|
}
|
|
|
|
|
|
|
|
-/* override sysctl_tcp_min_tso_segs */
|
|
|
|
-__bpf_kfunc static u32 bbr_min_tso_segs(struct sock *sk)
|
|
|
|
-{
|
|
|
|
- return READ_ONCE(sk->sk_pacing_rate) < (bbr_min_tso_rate >> 3) ? 1 : 2;
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Return the number of segments BBR would like in a TSO/GSO skb, given
|
|
|
|
- * a particular max gso size as a constraint.
|
|
|
|
+/* Return the number of segments BBR would like in a TSO/GSO skb, given a
|
|
|
|
+ * particular max gso size as a constraint. TODO: make this simpler and more
|
|
|
|
+ * consistent by switching bbr to just call tcp_tso_autosize().
|
|
|
|
*/
|
|
|
|
static u32 bbr_tso_segs_generic(struct sock *sk, unsigned int mss_now,
|
|
|
|
u32 gso_max_size)
|
|
|
|
{
|
|
|
|
- u32 segs;
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 segs, r;
|
|
|
|
u64 bytes;
|
|
|
|
|
|
|
|
/* Budget a TSO/GSO burst size allowance based on bw (pacing_rate). */
|
|
|
|
bytes = READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift);
|
|
|
|
|
|
|
|
+ /* Budget a TSO/GSO burst size allowance based on min_rtt. For every
|
|
|
|
+ * K = 2^tso_rtt_shift microseconds of min_rtt, halve the burst.
|
|
|
|
+ * The min_rtt-based burst allowance is: 64 KBytes / 2^(min_rtt/K)
|
|
|
|
+ */
|
|
|
|
+ if (bbr_param(sk, tso_rtt_shift)) {
|
|
|
|
+ r = bbr->min_rtt_us >> bbr_param(sk, tso_rtt_shift);
|
|
|
|
+ if (r < BITS_PER_TYPE(u32)) /* prevent undefined behavior */
|
|
|
|
+ bytes += GSO_LEGACY_MAX_SIZE >> r;
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
bytes = min_t(u32, bytes, gso_max_size - 1 - MAX_TCP_HEADER);
|
|
|
|
- segs = max_t(u32, bytes / mss_now, bbr_min_tso_segs(sk));
|
|
|
|
+ segs = max_t(u32, bytes / mss_now,
|
|
|
|
+ sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
|
|
|
|
return segs;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Custom tcp_tso_autosize() for BBR, used at transmit time to cap skb size. */
|
|
|
|
-static u32 bbr_tso_segs(struct sock *sk, unsigned int mss_now)
|
|
|
|
+__bpf_kfunc static u32 bbr_tso_segs(struct sock *sk, unsigned int mss_now)
|
|
|
|
{
|
|
|
|
return bbr_tso_segs_generic(sk, mss_now, sk->sk_gso_max_size);
|
|
|
|
}
|
|
|
|
@@ -329,7 +513,7 @@ static u32 bbr_tso_segs_goal(struct sock
|
|
|
|
{
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
|
|
|
|
- return bbr_tso_segs_generic(sk, tp->mss_cache, GSO_MAX_SIZE);
|
|
|
|
+ return bbr_tso_segs_generic(sk, tp->mss_cache, GSO_LEGACY_MAX_SIZE);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Save "last known good" cwnd so we can restore it after losses or PROBE_RTT */
|
|
|
|
@@ -349,7 +533,9 @@ __bpf_kfunc static void bbr_cwnd_event(s
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
|
|
|
|
- if (event == CA_EVENT_TX_START && tp->app_limited) {
|
|
|
|
+ if (event == CA_EVENT_TX_START) {
|
|
|
|
+ if (!tp->app_limited)
|
|
|
|
+ return;
|
|
|
|
bbr->idle_restart = 1;
|
|
|
|
bbr->ack_epoch_mstamp = tp->tcp_mstamp;
|
|
|
|
bbr->ack_epoch_acked = 0;
|
|
|
|
@@ -360,6 +546,16 @@ __bpf_kfunc static void bbr_cwnd_event(s
|
|
|
|
bbr_set_pacing_rate(sk, bbr_bw(sk), BBR_UNIT);
|
|
|
|
else if (bbr->mode == BBR_PROBE_RTT)
|
|
|
|
bbr_check_probe_rtt_done(sk);
|
|
|
|
+ } else if ((event == CA_EVENT_ECN_IS_CE ||
|
|
|
|
+ event == CA_EVENT_ECN_NO_CE) &&
|
|
|
|
+ bbr_can_use_ecn(sk) &&
|
|
|
|
+ bbr_param(sk, precise_ece_ack)) {
|
|
|
|
+ u32 state = bbr->ce_state;
|
|
|
|
+ dctcp_ece_ack_update(sk, event, &bbr->prior_rcv_nxt, &state);
|
|
|
|
+ bbr->ce_state = state;
|
|
|
|
+ } else if (event == CA_EVENT_TLP_RECOVERY &&
|
|
|
|
+ bbr_param(sk, loss_probe_recovery)) {
|
|
|
|
+ bbr_run_loss_probe_recovery(sk);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
@@ -382,10 +578,10 @@ static u32 bbr_bdp(struct sock *sk, u32
|
|
|
|
* default. This should only happen when the connection is not using TCP
|
|
|
|
* timestamps and has retransmitted all of the SYN/SYNACK/data packets
|
|
|
|
* ACKed so far. In this case, an RTO can cut cwnd to 1, in which
|
|
|
|
- * case we need to slow-start up toward something safe: TCP_INIT_CWND.
|
|
|
|
+ * case we need to slow-start up toward something safe: initial cwnd.
|
|
|
|
*/
|
|
|
|
if (unlikely(bbr->min_rtt_us == ~0U)) /* no valid RTT samples yet? */
|
|
|
|
- return TCP_INIT_CWND; /* be safe: cap at default initial cwnd*/
|
|
|
|
+ return bbr->init_cwnd; /* be safe: cap at initial cwnd */
|
|
|
|
|
|
|
|
w = (u64)bw * bbr->min_rtt_us;
|
|
|
|
|
|
|
|
@@ -402,23 +598,23 @@ static u32 bbr_bdp(struct sock *sk, u32
|
|
|
|
* - one skb in sending host Qdisc,
|
|
|
|
* - one skb in sending host TSO/GSO engine
|
|
|
|
* - one skb being received by receiver host LRO/GRO/delayed-ACK engine
|
|
|
|
- * Don't worry, at low rates (bbr_min_tso_rate) this won't bloat cwnd because
|
|
|
|
- * in such cases tso_segs_goal is 1. The minimum cwnd is 4 packets,
|
|
|
|
+ * Don't worry, at low rates this won't bloat cwnd because
|
|
|
|
+ * in such cases tso_segs_goal is small. The minimum cwnd is 4 packets,
|
|
|
|
* which allows 2 outstanding 2-packet sequences, to try to keep pipe
|
|
|
|
* full even with ACK-every-other-packet delayed ACKs.
|
|
|
|
*/
|
|
|
|
static u32 bbr_quantization_budget(struct sock *sk, u32 cwnd)
|
|
|
|
{
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 tso_segs_goal;
|
|
|
|
|
|
|
|
- /* Allow enough full-sized skbs in flight to utilize end systems. */
|
|
|
|
- cwnd += 3 * bbr_tso_segs_goal(sk);
|
|
|
|
-
|
|
|
|
- /* Reduce delayed ACKs by rounding up cwnd to the next even number. */
|
|
|
|
- cwnd = (cwnd + 1) & ~1U;
|
|
|
|
+ tso_segs_goal = 3 * bbr_tso_segs_goal(sk);
|
|
|
|
|
|
|
|
+ /* Allow enough full-sized skbs in flight to utilize end systems. */
|
|
|
|
+ cwnd = max_t(u32, cwnd, tso_segs_goal);
|
|
|
|
+ cwnd = max_t(u32, cwnd, bbr_param(sk, cwnd_min_target));
|
|
|
|
/* Ensure gain cycling gets inflight above BDP even for small BDPs. */
|
|
|
|
- if (bbr->mode == BBR_PROBE_BW && bbr->cycle_idx == 0)
|
|
|
|
+ if (bbr->mode == BBR_PROBE_BW && bbr->cycle_idx == BBR_BW_PROBE_UP)
|
|
|
|
cwnd += 2;
|
|
|
|
|
|
|
|
return cwnd;
|
|
|
|
@@ -473,10 +669,10 @@ static u32 bbr_ack_aggregation_cwnd(stru
|
|
|
|
{
|
|
|
|
u32 max_aggr_cwnd, aggr_cwnd = 0;
|
|
|
|
|
|
|
|
- if (bbr_extra_acked_gain && bbr_full_bw_reached(sk)) {
|
|
|
|
+ if (bbr_param(sk, extra_acked_gain)) {
|
|
|
|
max_aggr_cwnd = ((u64)bbr_bw(sk) * bbr_extra_acked_max_us)
|
|
|
|
/ BW_UNIT;
|
|
|
|
- aggr_cwnd = (bbr_extra_acked_gain * bbr_extra_acked(sk))
|
|
|
|
+ aggr_cwnd = (bbr_param(sk, extra_acked_gain) * bbr_extra_acked(sk))
|
|
|
|
>> BBR_SCALE;
|
|
|
|
aggr_cwnd = min(aggr_cwnd, max_aggr_cwnd);
|
|
|
|
}
|
|
|
|
@@ -484,66 +680,27 @@ static u32 bbr_ack_aggregation_cwnd(stru
|
|
|
|
return aggr_cwnd;
|
|
|
|
}
|
|
|
|
|
|
|
|
-/* An optimization in BBR to reduce losses: On the first round of recovery, we
|
|
|
|
- * follow the packet conservation principle: send P packets per P packets acked.
|
|
|
|
- * After that, we slow-start and send at most 2*P packets per P packets acked.
|
|
|
|
- * After recovery finishes, or upon undo, we restore the cwnd we had when
|
|
|
|
- * recovery started (capped by the target cwnd based on estimated BDP).
|
|
|
|
- *
|
|
|
|
- * TODO(ycheng/ncardwell): implement a rate-based approach.
|
|
|
|
- */
|
|
|
|
-static bool bbr_set_cwnd_to_recover_or_restore(
|
|
|
|
- struct sock *sk, const struct rate_sample *rs, u32 acked, u32 *new_cwnd)
|
|
|
|
+/* Returns the cwnd for PROBE_RTT mode. */
|
|
|
|
+static u32 bbr_probe_rtt_cwnd(struct sock *sk)
|
|
|
|
{
|
|
|
|
- struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u8 prev_state = bbr->prev_ca_state, state = inet_csk(sk)->icsk_ca_state;
|
|
|
|
- u32 cwnd = tcp_snd_cwnd(tp);
|
|
|
|
-
|
|
|
|
- /* An ACK for P pkts should release at most 2*P packets. We do this
|
|
|
|
- * in two steps. First, here we deduct the number of lost packets.
|
|
|
|
- * Then, in bbr_set_cwnd() we slow start up toward the target cwnd.
|
|
|
|
- */
|
|
|
|
- if (rs->losses > 0)
|
|
|
|
- cwnd = max_t(s32, cwnd - rs->losses, 1);
|
|
|
|
-
|
|
|
|
- if (state == TCP_CA_Recovery && prev_state != TCP_CA_Recovery) {
|
|
|
|
- /* Starting 1st round of Recovery, so do packet conservation. */
|
|
|
|
- bbr->packet_conservation = 1;
|
|
|
|
- bbr->next_rtt_delivered = tp->delivered; /* start round now */
|
|
|
|
- /* Cut unused cwnd from app behavior, TSQ, or TSO deferral: */
|
|
|
|
- cwnd = tcp_packets_in_flight(tp) + acked;
|
|
|
|
- } else if (prev_state >= TCP_CA_Recovery && state < TCP_CA_Recovery) {
|
|
|
|
- /* Exiting loss recovery; restore cwnd saved before recovery. */
|
|
|
|
- cwnd = max(cwnd, bbr->prior_cwnd);
|
|
|
|
- bbr->packet_conservation = 0;
|
|
|
|
- }
|
|
|
|
- bbr->prev_ca_state = state;
|
|
|
|
-
|
|
|
|
- if (bbr->packet_conservation) {
|
|
|
|
- *new_cwnd = max(cwnd, tcp_packets_in_flight(tp) + acked);
|
|
|
|
- return true; /* yes, using packet conservation */
|
|
|
|
- }
|
|
|
|
- *new_cwnd = cwnd;
|
|
|
|
- return false;
|
|
|
|
+ return max_t(u32, bbr_param(sk, cwnd_min_target),
|
|
|
|
+ bbr_bdp(sk, bbr_bw(sk), bbr_param(sk, probe_rtt_cwnd_gain)));
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Slow-start up toward target cwnd (if bw estimate is growing, or packet loss
|
|
|
|
* has drawn us down below target), or snap down to target if we're above it.
|
|
|
|
*/
|
|
|
|
static void bbr_set_cwnd(struct sock *sk, const struct rate_sample *rs,
|
|
|
|
- u32 acked, u32 bw, int gain)
|
|
|
|
+ u32 acked, u32 bw, int gain, u32 cwnd,
|
|
|
|
+ struct bbr_context *ctx)
|
|
|
|
{
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u32 cwnd = tcp_snd_cwnd(tp), target_cwnd = 0;
|
|
|
|
+ u32 target_cwnd = 0;
|
|
|
|
|
|
|
|
if (!acked)
|
|
|
|
goto done; /* no packet fully ACKed; just apply caps */
|
|
|
|
|
|
|
|
- if (bbr_set_cwnd_to_recover_or_restore(sk, rs, acked, &cwnd))
|
|
|
|
- goto done;
|
|
|
|
-
|
|
|
|
target_cwnd = bbr_bdp(sk, bw, gain);
|
|
|
|
|
|
|
|
/* Increment the cwnd to account for excess ACKed data that seems
|
|
|
|
@@ -552,74 +709,26 @@ static void bbr_set_cwnd(struct sock *sk
|
|
|
|
target_cwnd += bbr_ack_aggregation_cwnd(sk);
|
|
|
|
target_cwnd = bbr_quantization_budget(sk, target_cwnd);
|
|
|
|
|
|
|
|
- /* If we're below target cwnd, slow start cwnd toward target cwnd. */
|
|
|
|
- if (bbr_full_bw_reached(sk)) /* only cut cwnd if we filled the pipe */
|
|
|
|
- cwnd = min(cwnd + acked, target_cwnd);
|
|
|
|
- else if (cwnd < target_cwnd || tp->delivered < TCP_INIT_CWND)
|
|
|
|
- cwnd = cwnd + acked;
|
|
|
|
- cwnd = max(cwnd, bbr_cwnd_min_target);
|
|
|
|
+ /* Update cwnd and enable fast path if cwnd reaches target_cwnd. */
|
|
|
|
+ bbr->try_fast_path = 0;
|
|
|
|
+ if (bbr_full_bw_reached(sk)) { /* only cut cwnd if we filled the pipe */
|
|
|
|
+ cwnd += acked;
|
|
|
|
+ if (cwnd >= target_cwnd) {
|
|
|
|
+ cwnd = target_cwnd;
|
|
|
|
+ bbr->try_fast_path = 1;
|
|
|
|
+ }
|
|
|
|
+ } else if (cwnd < target_cwnd || cwnd < 2 * bbr->init_cwnd) {
|
|
|
|
+ cwnd += acked;
|
|
|
|
+ } else {
|
|
|
|
+ bbr->try_fast_path = 1;
|
|
|
|
+ }
|
|
|
|
|
|
|
|
+ cwnd = max_t(u32, cwnd, bbr_param(sk, cwnd_min_target));
|
|
|
|
done:
|
|
|
|
- tcp_snd_cwnd_set(tp, min(cwnd, tp->snd_cwnd_clamp)); /* apply global cap */
|
|
|
|
+ tcp_snd_cwnd_set(tp, min(cwnd, tp->snd_cwnd_clamp)); /* global cap */
|
|
|
|
if (bbr->mode == BBR_PROBE_RTT) /* drain queue, refresh min_rtt */
|
|
|
|
- tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), bbr_cwnd_min_target));
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* End cycle phase if it's time and/or we hit the phase's in-flight target. */
|
|
|
|
-static bool bbr_is_next_cycle_phase(struct sock *sk,
|
|
|
|
- const struct rate_sample *rs)
|
|
|
|
-{
|
|
|
|
- struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- bool is_full_length =
|
|
|
|
- tcp_stamp_us_delta(tp->delivered_mstamp, bbr->cycle_mstamp) >
|
|
|
|
- bbr->min_rtt_us;
|
|
|
|
- u32 inflight, bw;
|
|
|
|
-
|
|
|
|
- /* The pacing_gain of 1.0 paces at the estimated bw to try to fully
|
|
|
|
- * use the pipe without increasing the queue.
|
|
|
|
- */
|
|
|
|
- if (bbr->pacing_gain == BBR_UNIT)
|
|
|
|
- return is_full_length; /* just use wall clock time */
|
|
|
|
-
|
|
|
|
- inflight = bbr_packets_in_net_at_edt(sk, rs->prior_in_flight);
|
|
|
|
- bw = bbr_max_bw(sk);
|
|
|
|
-
|
|
|
|
- /* A pacing_gain > 1.0 probes for bw by trying to raise inflight to at
|
|
|
|
- * least pacing_gain*BDP; this may take more than min_rtt if min_rtt is
|
|
|
|
- * small (e.g. on a LAN). We do not persist if packets are lost, since
|
|
|
|
- * a path with small buffers may not hold that much.
|
|
|
|
- */
|
|
|
|
- if (bbr->pacing_gain > BBR_UNIT)
|
|
|
|
- return is_full_length &&
|
|
|
|
- (rs->losses || /* perhaps pacing_gain*BDP won't fit */
|
|
|
|
- inflight >= bbr_inflight(sk, bw, bbr->pacing_gain));
|
|
|
|
-
|
|
|
|
- /* A pacing_gain < 1.0 tries to drain extra queue we added if bw
|
|
|
|
- * probing didn't find more bw. If inflight falls to match BDP then we
|
|
|
|
- * estimate queue is drained; persisting would underutilize the pipe.
|
|
|
|
- */
|
|
|
|
- return is_full_length ||
|
|
|
|
- inflight <= bbr_inflight(sk, bw, BBR_UNIT);
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-static void bbr_advance_cycle_phase(struct sock *sk)
|
|
|
|
-{
|
|
|
|
- struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
-
|
|
|
|
- bbr->cycle_idx = (bbr->cycle_idx + 1) & (CYCLE_LEN - 1);
|
|
|
|
- bbr->cycle_mstamp = tp->delivered_mstamp;
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Gain cycling: cycle pacing gain to converge to fair share of available bw. */
|
|
|
|
-static void bbr_update_cycle_phase(struct sock *sk,
|
|
|
|
- const struct rate_sample *rs)
|
|
|
|
-{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
-
|
|
|
|
- if (bbr->mode == BBR_PROBE_BW && bbr_is_next_cycle_phase(sk, rs))
|
|
|
|
- bbr_advance_cycle_phase(sk);
|
|
|
|
+ tcp_snd_cwnd_set(tp, min_t(u32, tcp_snd_cwnd(tp),
|
|
|
|
+ bbr_probe_rtt_cwnd(sk)));
|
|
|
|
}
|
|
|
|
|
|
|
|
static void bbr_reset_startup_mode(struct sock *sk)
|
|
|
|
@@ -629,191 +738,49 @@ static void bbr_reset_startup_mode(struc
|
|
|
|
bbr->mode = BBR_STARTUP;
|
|
|
|
}
|
|
|
|
|
|
|
|
-static void bbr_reset_probe_bw_mode(struct sock *sk)
|
|
|
|
-{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
-
|
|
|
|
- bbr->mode = BBR_PROBE_BW;
|
|
|
|
- bbr->cycle_idx = CYCLE_LEN - 1 - get_random_u32_below(bbr_cycle_rand);
|
|
|
|
- bbr_advance_cycle_phase(sk); /* flip to next phase of gain cycle */
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-static void bbr_reset_mode(struct sock *sk)
|
|
|
|
-{
|
|
|
|
- if (!bbr_full_bw_reached(sk))
|
|
|
|
- bbr_reset_startup_mode(sk);
|
|
|
|
- else
|
|
|
|
- bbr_reset_probe_bw_mode(sk);
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Start a new long-term sampling interval. */
|
|
|
|
-static void bbr_reset_lt_bw_sampling_interval(struct sock *sk)
|
|
|
|
-{
|
|
|
|
- struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
-
|
|
|
|
- bbr->lt_last_stamp = div_u64(tp->delivered_mstamp, USEC_PER_MSEC);
|
|
|
|
- bbr->lt_last_delivered = tp->delivered;
|
|
|
|
- bbr->lt_last_lost = tp->lost;
|
|
|
|
- bbr->lt_rtt_cnt = 0;
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Completely reset long-term bandwidth sampling. */
|
|
|
|
-static void bbr_reset_lt_bw_sampling(struct sock *sk)
|
|
|
|
-{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
-
|
|
|
|
- bbr->lt_bw = 0;
|
|
|
|
- bbr->lt_use_bw = 0;
|
|
|
|
- bbr->lt_is_sampling = false;
|
|
|
|
- bbr_reset_lt_bw_sampling_interval(sk);
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Long-term bw sampling interval is done. Estimate whether we're policed. */
|
|
|
|
-static void bbr_lt_bw_interval_done(struct sock *sk, u32 bw)
|
|
|
|
-{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u32 diff;
|
|
|
|
-
|
|
|
|
- if (bbr->lt_bw) { /* do we have bw from a previous interval? */
|
|
|
|
- /* Is new bw close to the lt_bw from the previous interval? */
|
|
|
|
- diff = abs(bw - bbr->lt_bw);
|
|
|
|
- if ((diff * BBR_UNIT <= bbr_lt_bw_ratio * bbr->lt_bw) ||
|
|
|
|
- (bbr_rate_bytes_per_sec(sk, diff, BBR_UNIT) <=
|
|
|
|
- bbr_lt_bw_diff)) {
|
|
|
|
- /* All criteria are met; estimate we're policed. */
|
|
|
|
- bbr->lt_bw = (bw + bbr->lt_bw) >> 1; /* avg 2 intvls */
|
|
|
|
- bbr->lt_use_bw = 1;
|
|
|
|
- bbr->pacing_gain = BBR_UNIT; /* try to avoid drops */
|
|
|
|
- bbr->lt_rtt_cnt = 0;
|
|
|
|
- return;
|
|
|
|
- }
|
|
|
|
- }
|
|
|
|
- bbr->lt_bw = bw;
|
|
|
|
- bbr_reset_lt_bw_sampling_interval(sk);
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Token-bucket traffic policers are common (see "An Internet-Wide Analysis of
|
|
|
|
- * Traffic Policing", SIGCOMM 2016). BBR detects token-bucket policers and
|
|
|
|
- * explicitly models their policed rate, to reduce unnecessary losses. We
|
|
|
|
- * estimate that we're policed if we see 2 consecutive sampling intervals with
|
|
|
|
- * consistent throughput and high packet loss. If we think we're being policed,
|
|
|
|
- * set lt_bw to the "long-term" average delivery rate from those 2 intervals.
|
|
|
|
+/* See if we have reached next round trip. Upon start of the new round,
|
|
|
|
+ * returns packets delivered since previous round start plus this ACK.
|
|
|
|
*/
|
|
|
|
-static void bbr_lt_bw_sampling(struct sock *sk, const struct rate_sample *rs)
|
|
|
|
+static u32 bbr_update_round_start(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs, struct bbr_context *ctx)
|
|
|
|
{
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u32 lost, delivered;
|
|
|
|
- u64 bw;
|
|
|
|
- u32 t;
|
|
|
|
-
|
|
|
|
- if (bbr->lt_use_bw) { /* already using long-term rate, lt_bw? */
|
|
|
|
- if (bbr->mode == BBR_PROBE_BW && bbr->round_start &&
|
|
|
|
- ++bbr->lt_rtt_cnt >= bbr_lt_bw_max_rtts) {
|
|
|
|
- bbr_reset_lt_bw_sampling(sk); /* stop using lt_bw */
|
|
|
|
- bbr_reset_probe_bw_mode(sk); /* restart gain cycling */
|
|
|
|
- }
|
|
|
|
- return;
|
|
|
|
- }
|
|
|
|
-
|
|
|
|
- /* Wait for the first loss before sampling, to let the policer exhaust
|
|
|
|
- * its tokens and estimate the steady-state rate allowed by the policer.
|
|
|
|
- * Starting samples earlier includes bursts that over-estimate the bw.
|
|
|
|
- */
|
|
|
|
- if (!bbr->lt_is_sampling) {
|
|
|
|
- if (!rs->losses)
|
|
|
|
- return;
|
|
|
|
- bbr_reset_lt_bw_sampling_interval(sk);
|
|
|
|
- bbr->lt_is_sampling = true;
|
|
|
|
- }
|
|
|
|
-
|
|
|
|
- /* To avoid underestimates, reset sampling if we run out of data. */
|
|
|
|
- if (rs->is_app_limited) {
|
|
|
|
- bbr_reset_lt_bw_sampling(sk);
|
|
|
|
- return;
|
|
|
|
- }
|
|
|
|
-
|
|
|
|
- if (bbr->round_start)
|
|
|
|
- bbr->lt_rtt_cnt++; /* count round trips in this interval */
|
|
|
|
- if (bbr->lt_rtt_cnt < bbr_lt_intvl_min_rtts)
|
|
|
|
- return; /* sampling interval needs to be longer */
|
|
|
|
- if (bbr->lt_rtt_cnt > 4 * bbr_lt_intvl_min_rtts) {
|
|
|
|
- bbr_reset_lt_bw_sampling(sk); /* interval is too long */
|
|
|
|
- return;
|
|
|
|
- }
|
|
|
|
-
|
|
|
|
- /* End sampling interval when a packet is lost, so we estimate the
|
|
|
|
- * policer tokens were exhausted. Stopping the sampling before the
|
|
|
|
- * tokens are exhausted under-estimates the policed rate.
|
|
|
|
- */
|
|
|
|
- if (!rs->losses)
|
|
|
|
- return;
|
|
|
|
-
|
|
|
|
- /* Calculate packets lost and delivered in sampling interval. */
|
|
|
|
- lost = tp->lost - bbr->lt_last_lost;
|
|
|
|
- delivered = tp->delivered - bbr->lt_last_delivered;
|
|
|
|
- /* Is loss rate (lost/delivered) >= lt_loss_thresh? If not, wait. */
|
|
|
|
- if (!delivered || (lost << BBR_SCALE) < bbr_lt_loss_thresh * delivered)
|
|
|
|
- return;
|
|
|
|
-
|
|
|
|
- /* Find average delivery rate in this sampling interval. */
|
|
|
|
- t = div_u64(tp->delivered_mstamp, USEC_PER_MSEC) - bbr->lt_last_stamp;
|
|
|
|
- if ((s32)t < 1)
|
|
|
|
- return; /* interval is less than one ms, so wait */
|
|
|
|
- /* Check if can multiply without overflow */
|
|
|
|
- if (t >= ~0U / USEC_PER_MSEC) {
|
|
|
|
- bbr_reset_lt_bw_sampling(sk); /* interval too long; reset */
|
|
|
|
- return;
|
|
|
|
- }
|
|
|
|
- t *= USEC_PER_MSEC;
|
|
|
|
- bw = (u64)delivered * BW_UNIT;
|
|
|
|
- do_div(bw, t);
|
|
|
|
- bbr_lt_bw_interval_done(sk, bw);
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* Estimate the bandwidth based on how fast packets are delivered */
|
|
|
|
-static void bbr_update_bw(struct sock *sk, const struct rate_sample *rs)
|
|
|
|
-{
|
|
|
|
- struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u64 bw;
|
|
|
|
+ u32 round_delivered = 0;
|
|
|
|
|
|
|
|
bbr->round_start = 0;
|
|
|
|
- if (rs->delivered < 0 || rs->interval_us <= 0)
|
|
|
|
- return; /* Not a valid observation */
|
|
|
|
|
|
|
|
/* See if we've reached the next RTT */
|
|
|
|
- if (!before(rs->prior_delivered, bbr->next_rtt_delivered)) {
|
|
|
|
+ if (rs->interval_us > 0 &&
|
|
|
|
+ !before(rs->prior_delivered, bbr->next_rtt_delivered)) {
|
|
|
|
+ round_delivered = tp->delivered - bbr->next_rtt_delivered;
|
|
|
|
bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
- bbr->rtt_cnt++;
|
|
|
|
bbr->round_start = 1;
|
|
|
|
- bbr->packet_conservation = 0;
|
|
|
|
}
|
|
|
|
+ return round_delivered;
|
|
|
|
+}
|
|
|
|
|
|
|
|
- bbr_lt_bw_sampling(sk, rs);
|
|
|
|
+/* Calculate the bandwidth based on how fast packets are delivered */
|
|
|
|
+static void bbr_calculate_bw_sample(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs, struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ u64 bw = 0;
|
|
|
|
|
|
|
|
/* Divide delivered by the interval to find a (lower bound) bottleneck
|
|
|
|
* bandwidth sample. Delivered is in packets and interval_us in uS and
|
|
|
|
* ratio will be <<1 for most connections. So delivered is first scaled.
|
|
|
|
+ * Round up to allow growth at low rates, even with integer division.
|
|
|
|
*/
|
|
|
|
- bw = div64_long((u64)rs->delivered * BW_UNIT, rs->interval_us);
|
|
|
|
+ if (rs->interval_us > 0) {
|
|
|
|
+ if (WARN_ONCE(rs->delivered < 0,
|
|
|
|
+ "negative delivered: %d interval_us: %ld\n",
|
|
|
|
+ rs->delivered, rs->interval_us))
|
|
|
|
+ return;
|
|
|
|
|
|
|
|
- /* If this sample is application-limited, it is likely to have a very
|
|
|
|
- * low delivered count that represents application behavior rather than
|
|
|
|
- * the available network rate. Such a sample could drag down estimated
|
|
|
|
- * bw, causing needless slow-down. Thus, to continue to send at the
|
|
|
|
- * last measured network rate, we filter out app-limited samples unless
|
|
|
|
- * they describe the path bw at least as well as our bw model.
|
|
|
|
- *
|
|
|
|
- * So the goal during app-limited phase is to proceed with the best
|
|
|
|
- * network rate no matter how long. We automatically leave this
|
|
|
|
- * phase when app writes faster than the network can deliver :)
|
|
|
|
- */
|
|
|
|
- if (!rs->is_app_limited || bw >= bbr_max_bw(sk)) {
|
|
|
|
- /* Incorporate new sample into our max bw filter. */
|
|
|
|
- minmax_running_max(&bbr->bw, bbr_bw_rtts, bbr->rtt_cnt, bw);
|
|
|
|
+ bw = DIV_ROUND_UP_ULL((u64)rs->delivered * BW_UNIT, rs->interval_us);
|
|
|
|
}
|
|
|
|
+
|
|
|
|
+ ctx->sample_bw = bw;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Estimates the windowed max degree of ack aggregation.
|
|
|
|
@@ -827,7 +794,7 @@ static void bbr_update_bw(struct sock *s
|
|
|
|
*
|
|
|
|
* Max extra_acked is clamped by cwnd and bw * bbr_extra_acked_max_us (100 ms).
|
|
|
|
* Max filter is an approximate sliding window of 5-10 (packet timed) round
|
|
|
|
- * trips.
|
|
|
|
+ * trips for non-startup phase, and 1-2 round trips for startup.
|
|
|
|
*/
|
|
|
|
static void bbr_update_ack_aggregation(struct sock *sk,
|
|
|
|
const struct rate_sample *rs)
|
|
|
|
@@ -835,15 +802,19 @@ static void bbr_update_ack_aggregation(s
|
|
|
|
u32 epoch_us, expected_acked, extra_acked;
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ u32 extra_acked_win_rtts_thresh = bbr_param(sk, extra_acked_win_rtts);
|
|
|
|
|
|
|
|
- if (!bbr_extra_acked_gain || rs->acked_sacked <= 0 ||
|
|
|
|
+ if (!bbr_param(sk, extra_acked_gain) || rs->acked_sacked <= 0 ||
|
|
|
|
rs->delivered < 0 || rs->interval_us <= 0)
|
|
|
|
return;
|
|
|
|
|
|
|
|
if (bbr->round_start) {
|
|
|
|
bbr->extra_acked_win_rtts = min(0x1F,
|
|
|
|
bbr->extra_acked_win_rtts + 1);
|
|
|
|
- if (bbr->extra_acked_win_rtts >= bbr_extra_acked_win_rtts) {
|
|
|
|
+ if (!bbr_full_bw_reached(sk))
|
|
|
|
+ extra_acked_win_rtts_thresh = 1;
|
|
|
|
+ if (bbr->extra_acked_win_rtts >=
|
|
|
|
+ extra_acked_win_rtts_thresh) {
|
|
|
|
bbr->extra_acked_win_rtts = 0;
|
|
|
|
bbr->extra_acked_win_idx = bbr->extra_acked_win_idx ?
|
|
|
|
0 : 1;
|
|
|
|
@@ -877,49 +848,6 @@ static void bbr_update_ack_aggregation(s
|
|
|
|
bbr->extra_acked[bbr->extra_acked_win_idx] = extra_acked;
|
|
|
|
}
|
|
|
|
|
|
|
|
-/* Estimate when the pipe is full, using the change in delivery rate: BBR
|
|
|
|
- * estimates that STARTUP filled the pipe if the estimated bw hasn't changed by
|
|
|
|
- * at least bbr_full_bw_thresh (25%) after bbr_full_bw_cnt (3) non-app-limited
|
|
|
|
- * rounds. Why 3 rounds: 1: rwin autotuning grows the rwin, 2: we fill the
|
|
|
|
- * higher rwin, 3: we get higher delivery rate samples. Or transient
|
|
|
|
- * cross-traffic or radio noise can go away. CUBIC Hystart shares a similar
|
|
|
|
- * design goal, but uses delay and inter-ACK spacing instead of bandwidth.
|
|
|
|
- */
|
|
|
|
-static void bbr_check_full_bw_reached(struct sock *sk,
|
|
|
|
- const struct rate_sample *rs)
|
|
|
|
-{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u32 bw_thresh;
|
|
|
|
-
|
|
|
|
- if (bbr_full_bw_reached(sk) || !bbr->round_start || rs->is_app_limited)
|
|
|
|
- return;
|
|
|
|
-
|
|
|
|
- bw_thresh = (u64)bbr->full_bw * bbr_full_bw_thresh >> BBR_SCALE;
|
|
|
|
- if (bbr_max_bw(sk) >= bw_thresh) {
|
|
|
|
- bbr->full_bw = bbr_max_bw(sk);
|
|
|
|
- bbr->full_bw_cnt = 0;
|
|
|
|
- return;
|
|
|
|
- }
|
|
|
|
- ++bbr->full_bw_cnt;
|
|
|
|
- bbr->full_bw_reached = bbr->full_bw_cnt >= bbr_full_bw_cnt;
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
-/* If pipe is probably full, drain the queue and then enter steady-state. */
|
|
|
|
-static void bbr_check_drain(struct sock *sk, const struct rate_sample *rs)
|
|
|
|
-{
|
|
|
|
- struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
-
|
|
|
|
- if (bbr->mode == BBR_STARTUP && bbr_full_bw_reached(sk)) {
|
|
|
|
- bbr->mode = BBR_DRAIN; /* drain queue we created */
|
|
|
|
- tcp_sk(sk)->snd_ssthresh =
|
|
|
|
- bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT);
|
|
|
|
- } /* fall through to check if in-flight is already small: */
|
|
|
|
- if (bbr->mode == BBR_DRAIN &&
|
|
|
|
- bbr_packets_in_net_at_edt(sk, tcp_packets_in_flight(tcp_sk(sk))) <=
|
|
|
|
- bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT))
|
|
|
|
- bbr_reset_probe_bw_mode(sk); /* we estimate queue is drained */
|
|
|
|
-}
|
|
|
|
-
|
|
|
|
static void bbr_check_probe_rtt_done(struct sock *sk)
|
|
|
|
{
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
@@ -929,9 +857,9 @@ static void bbr_check_probe_rtt_done(str
|
|
|
|
after(tcp_jiffies32, bbr->probe_rtt_done_stamp)))
|
|
|
|
return;
|
|
|
|
|
|
|
|
- bbr->min_rtt_stamp = tcp_jiffies32; /* wait a while until PROBE_RTT */
|
|
|
|
+ bbr->probe_rtt_min_stamp = tcp_jiffies32; /* schedule next PROBE_RTT */
|
|
|
|
tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp), bbr->prior_cwnd));
|
|
|
|
- bbr_reset_mode(sk);
|
|
|
|
+ bbr_exit_probe_rtt(sk);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* The goal of PROBE_RTT mode is to have BBR flows cooperatively and
|
|
|
|
@@ -957,23 +885,35 @@ static void bbr_update_min_rtt(struct so
|
|
|
|
{
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- bool filter_expired;
|
|
|
|
+ bool probe_rtt_expired, min_rtt_expired;
|
|
|
|
+ u32 expire;
|
|
|
|
|
|
|
|
- /* Track min RTT seen in the min_rtt_win_sec filter window: */
|
|
|
|
- filter_expired = after(tcp_jiffies32,
|
|
|
|
- bbr->min_rtt_stamp + bbr_min_rtt_win_sec * HZ);
|
|
|
|
+ /* Track min RTT in probe_rtt_win_ms to time next PROBE_RTT state. */
|
|
|
|
+ expire = bbr->probe_rtt_min_stamp +
|
|
|
|
+ msecs_to_jiffies(bbr_param(sk, probe_rtt_win_ms));
|
|
|
|
+ probe_rtt_expired = after(tcp_jiffies32, expire);
|
|
|
|
if (rs->rtt_us >= 0 &&
|
|
|
|
- (rs->rtt_us < bbr->min_rtt_us ||
|
|
|
|
- (filter_expired && !rs->is_ack_delayed))) {
|
|
|
|
- bbr->min_rtt_us = rs->rtt_us;
|
|
|
|
- bbr->min_rtt_stamp = tcp_jiffies32;
|
|
|
|
+ (rs->rtt_us < bbr->probe_rtt_min_us ||
|
|
|
|
+ (probe_rtt_expired && !rs->is_ack_delayed))) {
|
|
|
|
+ bbr->probe_rtt_min_us = rs->rtt_us;
|
|
|
|
+ bbr->probe_rtt_min_stamp = tcp_jiffies32;
|
|
|
|
+ }
|
|
|
|
+ /* Track min RTT seen in the min_rtt_win_sec filter window: */
|
|
|
|
+ expire = bbr->min_rtt_stamp + bbr_param(sk, min_rtt_win_sec) * HZ;
|
|
|
|
+ min_rtt_expired = after(tcp_jiffies32, expire);
|
|
|
|
+ if (bbr->probe_rtt_min_us <= bbr->min_rtt_us ||
|
|
|
|
+ min_rtt_expired) {
|
|
|
|
+ bbr->min_rtt_us = bbr->probe_rtt_min_us;
|
|
|
|
+ bbr->min_rtt_stamp = bbr->probe_rtt_min_stamp;
|
|
|
|
}
|
|
|
|
|
|
|
|
- if (bbr_probe_rtt_mode_ms > 0 && filter_expired &&
|
|
|
|
+ if (bbr_param(sk, probe_rtt_mode_ms) > 0 && probe_rtt_expired &&
|
|
|
|
!bbr->idle_restart && bbr->mode != BBR_PROBE_RTT) {
|
|
|
|
bbr->mode = BBR_PROBE_RTT; /* dip, drain queue */
|
|
|
|
bbr_save_cwnd(sk); /* note cwnd so we can restore it */
|
|
|
|
bbr->probe_rtt_done_stamp = 0;
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_PROBE_STOPPING;
|
|
|
|
+ bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (bbr->mode == BBR_PROBE_RTT) {
|
|
|
|
@@ -982,9 +922,9 @@ static void bbr_update_min_rtt(struct so
|
|
|
|
(tp->delivered + tcp_packets_in_flight(tp)) ? : 1;
|
|
|
|
/* Maintain min packets in flight for max(200 ms, 1 round). */
|
|
|
|
if (!bbr->probe_rtt_done_stamp &&
|
|
|
|
- tcp_packets_in_flight(tp) <= bbr_cwnd_min_target) {
|
|
|
|
+ tcp_packets_in_flight(tp) <= bbr_probe_rtt_cwnd(sk)) {
|
|
|
|
bbr->probe_rtt_done_stamp = tcp_jiffies32 +
|
|
|
|
- msecs_to_jiffies(bbr_probe_rtt_mode_ms);
|
|
|
|
+ msecs_to_jiffies(bbr_param(sk, probe_rtt_mode_ms));
|
|
|
|
bbr->probe_rtt_round_done = 0;
|
|
|
|
bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
} else if (bbr->probe_rtt_done_stamp) {
|
|
|
|
@@ -1005,18 +945,20 @@ static void bbr_update_gains(struct sock
|
|
|
|
|
|
|
|
switch (bbr->mode) {
|
|
|
|
case BBR_STARTUP:
|
|
|
|
- bbr->pacing_gain = bbr_high_gain;
|
|
|
|
- bbr->cwnd_gain = bbr_high_gain;
|
|
|
|
+ bbr->pacing_gain = bbr_param(sk, startup_pacing_gain);
|
|
|
|
+ bbr->cwnd_gain = bbr_param(sk, startup_cwnd_gain);
|
|
|
|
break;
|
|
|
|
case BBR_DRAIN:
|
|
|
|
- bbr->pacing_gain = bbr_drain_gain; /* slow, to drain */
|
|
|
|
- bbr->cwnd_gain = bbr_high_gain; /* keep cwnd */
|
|
|
|
+ bbr->pacing_gain = bbr_param(sk, drain_gain); /* slow, to drain */
|
|
|
|
+ bbr->cwnd_gain = bbr_param(sk, startup_cwnd_gain); /* keep cwnd */
|
|
|
|
break;
|
|
|
|
case BBR_PROBE_BW:
|
|
|
|
- bbr->pacing_gain = (bbr->lt_use_bw ?
|
|
|
|
- BBR_UNIT :
|
|
|
|
- bbr_pacing_gain[bbr->cycle_idx]);
|
|
|
|
- bbr->cwnd_gain = bbr_cwnd_gain;
|
|
|
|
+ bbr->pacing_gain = bbr_pacing_gain[bbr->cycle_idx];
|
|
|
|
+ bbr->cwnd_gain = bbr_param(sk, cwnd_gain);
|
|
|
|
+ if (bbr_param(sk, bw_probe_cwnd_gain) &&
|
|
|
|
+ bbr->cycle_idx == BBR_BW_PROBE_UP)
|
|
|
|
+ bbr->cwnd_gain +=
|
|
|
|
+ BBR_UNIT * bbr_param(sk, bw_probe_cwnd_gain) / 4;
|
|
|
|
break;
|
|
|
|
case BBR_PROBE_RTT:
|
|
|
|
bbr->pacing_gain = BBR_UNIT;
|
|
|
|
@@ -1028,27 +970,1108 @@ static void bbr_update_gains(struct sock
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
-static void bbr_update_model(struct sock *sk, const struct rate_sample *rs)
|
|
|
|
+__bpf_kfunc static u32 bbr_sndbuf_expand(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ /* Provision 3 * cwnd since BBR may slow-start even during recovery. */
|
|
|
|
+ return 3;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Incorporate a new bw sample into the current window of our max filter. */
|
|
|
|
+static void bbr_take_max_bw_sample(struct sock *sk, u32 bw)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->bw_hi[1] = max(bw, bbr->bw_hi[1]);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Keep max of last 1-2 cycles. Each PROBE_BW cycle, flip filter window. */
|
|
|
|
+static void bbr_advance_max_bw_filter(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (!bbr->bw_hi[1])
|
|
|
|
+ return; /* no samples in this window; remember old window */
|
|
|
|
+ bbr->bw_hi[0] = bbr->bw_hi[1];
|
|
|
|
+ bbr->bw_hi[1] = 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Reset the estimator for reaching full bandwidth based on bw plateau. */
|
|
|
|
+static void bbr_reset_full_bw(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->full_bw = 0;
|
|
|
|
+ bbr->full_bw_cnt = 0;
|
|
|
|
+ bbr->full_bw_now = 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* How much do we want in flight? Our BDP, unless congestion cut cwnd. */
|
|
|
|
+static u32 bbr_target_inflight(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ u32 bdp = bbr_inflight(sk, bbr_bw(sk), BBR_UNIT);
|
|
|
|
+
|
|
|
|
+ return min(bdp, tcp_sk(sk)->snd_cwnd);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static bool bbr_is_probing_bandwidth(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ return (bbr->mode == BBR_STARTUP) ||
|
|
|
|
+ (bbr->mode == BBR_PROBE_BW &&
|
|
|
|
+ (bbr->cycle_idx == BBR_BW_PROBE_REFILL ||
|
|
|
|
+ bbr->cycle_idx == BBR_BW_PROBE_UP));
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Has the given amount of time elapsed since we marked the phase start? */
|
|
|
|
+static bool bbr_has_elapsed_in_phase(const struct sock *sk, u32 interval_us)
|
|
|
|
+{
|
|
|
|
+ const struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ const struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ return tcp_stamp_us_delta(tp->tcp_mstamp,
|
|
|
|
+ bbr->cycle_mstamp + interval_us) > 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static void bbr_handle_queue_too_high_in_startup(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 bdp; /* estimated BDP in packets, with quantization budget */
|
|
|
|
+
|
|
|
|
+ bbr->full_bw_reached = 1;
|
|
|
|
+
|
|
|
|
+ bdp = bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT);
|
|
|
|
+ bbr->inflight_hi = max(bdp, bbr->inflight_latest);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Exit STARTUP upon N consecutive rounds with ECN mark rate > ecn_thresh. */
|
|
|
|
+static void bbr_check_ecn_too_high_in_startup(struct sock *sk, u32 ce_ratio)
|
|
|
|
{
|
|
|
|
- bbr_update_bw(sk, rs);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (bbr_full_bw_reached(sk) || !bbr->ecn_eligible ||
|
|
|
|
+ !bbr_param(sk, full_ecn_cnt) || !bbr_param(sk, ecn_thresh))
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ if (ce_ratio >= bbr_param(sk, ecn_thresh))
|
|
|
|
+ bbr->startup_ecn_rounds++;
|
|
|
|
+ else
|
|
|
|
+ bbr->startup_ecn_rounds = 0;
|
|
|
|
+
|
|
|
|
+ if (bbr->startup_ecn_rounds >= bbr_param(sk, full_ecn_cnt)) {
|
|
|
|
+ bbr_handle_queue_too_high_in_startup(sk);
|
|
|
|
+ return;
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Updates ecn_alpha and returns ce_ratio. -1 if not available. */
|
|
|
|
+static int bbr_update_ecn_alpha(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct net *net = sock_net(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ s32 delivered, delivered_ce;
|
|
|
|
+ u64 alpha, ce_ratio;
|
|
|
|
+ u32 gain;
|
|
|
|
+ bool want_ecn_alpha;
|
|
|
|
+
|
|
|
|
+ /* See if we should use ECN sender logic for this connection. */
|
|
|
|
+ if (!bbr->ecn_eligible && bbr_can_use_ecn(sk) &&
|
|
|
|
+ bbr_param(sk, ecn_factor) &&
|
|
|
|
+ (bbr->min_rtt_us <= bbr_ecn_max_rtt_us ||
|
|
|
|
+ !bbr_ecn_max_rtt_us))
|
|
|
|
+ bbr->ecn_eligible = 1;
|
|
|
|
+
|
|
|
|
+ /* Skip updating alpha only if not ECN-eligible and PLB is disabled. */
|
|
|
|
+ want_ecn_alpha = (bbr->ecn_eligible ||
|
|
|
|
+ (bbr_can_use_ecn(sk) &&
|
|
|
|
+ READ_ONCE(net->ipv4.sysctl_tcp_plb_enabled)));
|
|
|
|
+ if (!want_ecn_alpha)
|
|
|
|
+ return -1;
|
|
|
|
+
|
|
|
|
+ delivered = tp->delivered - bbr->alpha_last_delivered;
|
|
|
|
+ delivered_ce = tp->delivered_ce - bbr->alpha_last_delivered_ce;
|
|
|
|
+
|
|
|
|
+ if (delivered == 0 || /* avoid divide by zero */
|
|
|
|
+ WARN_ON_ONCE(delivered < 0 || delivered_ce < 0)) /* backwards? */
|
|
|
|
+ return -1;
|
|
|
|
+
|
|
|
|
+ BUILD_BUG_ON(BBR_SCALE != TCP_PLB_SCALE);
|
|
|
|
+ ce_ratio = (u64)delivered_ce << BBR_SCALE;
|
|
|
|
+ do_div(ce_ratio, delivered);
|
|
|
|
+
|
|
|
|
+ gain = bbr_param(sk, ecn_alpha_gain);
|
|
|
|
+ alpha = ((BBR_UNIT - gain) * bbr->ecn_alpha) >> BBR_SCALE;
|
|
|
|
+ alpha += (gain * ce_ratio) >> BBR_SCALE;
|
|
|
|
+ bbr->ecn_alpha = min_t(u32, alpha, BBR_UNIT);
|
|
|
|
+
|
|
|
|
+ bbr->alpha_last_delivered = tp->delivered;
|
|
|
|
+ bbr->alpha_last_delivered_ce = tp->delivered_ce;
|
|
|
|
+
|
|
|
|
+ bbr_check_ecn_too_high_in_startup(sk, ce_ratio);
|
|
|
|
+ return (int)ce_ratio;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Protective Load Balancing (PLB). PLB rehashes outgoing data (to a new IPv6
|
|
|
|
+ * flow label) if it encounters sustained congestion in the form of ECN marks.
|
|
|
|
+ */
|
|
|
|
+static void bbr_plb(struct sock *sk, const struct rate_sample *rs, int ce_ratio)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (bbr->round_start && ce_ratio >= 0)
|
|
|
|
+ tcp_plb_update_state(sk, &bbr->plb, ce_ratio);
|
|
|
|
+
|
|
|
|
+ tcp_plb_check_rehash(sk, &bbr->plb);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Each round trip of BBR_BW_PROBE_UP, double volume of probing data. */
|
|
|
|
+static void bbr_raise_inflight_hi_slope(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 growth_this_round, cnt;
|
|
|
|
+
|
|
|
|
+ /* Calculate "slope": packets S/Acked per inflight_hi increment. */
|
|
|
|
+ growth_this_round = 1 << bbr->bw_probe_up_rounds;
|
|
|
|
+ bbr->bw_probe_up_rounds = min(bbr->bw_probe_up_rounds + 1, 30);
|
|
|
|
+ cnt = tcp_snd_cwnd(tp) / growth_this_round;
|
|
|
|
+ cnt = max(cnt, 1U);
|
|
|
|
+ bbr->bw_probe_up_cnt = cnt;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* In BBR_BW_PROBE_UP, not seeing high loss/ECN/queue, so raise inflight_hi. */
|
|
|
|
+static void bbr_probe_inflight_hi_upward(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 delta;
|
|
|
|
+
|
|
|
|
+ if (!tp->is_cwnd_limited || tcp_snd_cwnd(tp) < bbr->inflight_hi)
|
|
|
|
+ return; /* not fully using inflight_hi, so don't grow it */
|
|
|
|
+
|
|
|
|
+ /* For each bw_probe_up_cnt packets ACKed, increase inflight_hi by 1. */
|
|
|
|
+ bbr->bw_probe_up_acks += rs->acked_sacked;
|
|
|
|
+ if (bbr->bw_probe_up_acks >= bbr->bw_probe_up_cnt) {
|
|
|
|
+ delta = bbr->bw_probe_up_acks / bbr->bw_probe_up_cnt;
|
|
|
|
+ bbr->bw_probe_up_acks -= delta * bbr->bw_probe_up_cnt;
|
|
|
|
+ bbr->inflight_hi += delta;
|
|
|
|
+ bbr->try_fast_path = 0; /* Need to update cwnd */
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ if (bbr->round_start)
|
|
|
|
+ bbr_raise_inflight_hi_slope(sk);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Does loss/ECN rate for this sample say inflight is "too high"?
|
|
|
|
+ * This is used by both the bbr_check_loss_too_high_in_startup() function,
|
|
|
|
+ * which can be used in either v1 or v2, and the PROBE_UP phase of v2, which
|
|
|
|
+ * uses it to notice when loss/ECN rates suggest inflight is too high.
|
|
|
|
+ */
|
|
|
|
+static bool bbr_is_inflight_too_high(const struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs)
|
|
|
|
+{
|
|
|
|
+ const struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 loss_thresh, ecn_thresh;
|
|
|
|
+
|
|
|
|
+ if (rs->lost > 0 && rs->tx_in_flight) {
|
|
|
|
+ loss_thresh = (u64)rs->tx_in_flight * bbr_param(sk, loss_thresh) >>
|
|
|
|
+ BBR_SCALE;
|
|
|
|
+ if (rs->lost > loss_thresh) {
|
|
|
|
+ return true;
|
|
|
|
+ }
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ if (rs->delivered_ce > 0 && rs->delivered > 0 &&
|
|
|
|
+ bbr->ecn_eligible && bbr_param(sk, ecn_thresh)) {
|
|
|
|
+ ecn_thresh = (u64)rs->delivered * bbr_param(sk, ecn_thresh) >>
|
|
|
|
+ BBR_SCALE;
|
|
|
|
+ if (rs->delivered_ce > ecn_thresh) {
|
|
|
|
+ return true;
|
|
|
|
+ }
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ return false;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Calculate the tx_in_flight level that corresponded to excessive loss.
|
|
|
|
+ * We find "lost_prefix" segs of the skb where loss rate went too high,
|
|
|
|
+ * by solving for "lost_prefix" in the following equation:
|
|
|
|
+ * lost / inflight >= loss_thresh
|
|
|
|
+ * (lost_prev + lost_prefix) / (inflight_prev + lost_prefix) >= loss_thresh
|
|
|
|
+ * Then we take that equation, convert it to fixed point, and
|
|
|
|
+ * round up to the nearest packet.
|
|
|
|
+ */
|
|
|
|
+static u32 bbr_inflight_hi_from_lost_skb(const struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs,
|
|
|
|
+ const struct sk_buff *skb)
|
|
|
|
+{
|
|
|
|
+ const struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ u32 loss_thresh = bbr_param(sk, loss_thresh);
|
|
|
|
+ u32 pcount, divisor, inflight_hi;
|
|
|
|
+ s32 inflight_prev, lost_prev;
|
|
|
|
+ u64 loss_budget, lost_prefix;
|
|
|
|
+
|
|
|
|
+ pcount = tcp_skb_pcount(skb);
|
|
|
|
+
|
|
|
|
+ /* How much data was in flight before this skb? */
|
|
|
|
+ inflight_prev = rs->tx_in_flight - pcount;
|
|
|
|
+ if (inflight_prev < 0) {
|
|
|
|
+ WARN_ONCE(tcp_skb_tx_in_flight_is_suspicious(
|
|
|
|
+ pcount,
|
|
|
|
+ TCP_SKB_CB(skb)->sacked,
|
|
|
|
+ rs->tx_in_flight),
|
|
|
|
+ "tx_in_flight: %u pcount: %u reneg: %u",
|
|
|
|
+ rs->tx_in_flight, pcount, tcp_sk(sk)->is_sack_reneg);
|
|
|
|
+ return ~0U;
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ /* How much inflight data was marked lost before this skb? */
|
|
|
|
+ lost_prev = rs->lost - pcount;
|
|
|
|
+ if (WARN_ONCE(lost_prev < 0,
|
|
|
|
+ "cwnd: %u ca: %d out: %u lost: %u pif: %u "
|
|
|
|
+ "tx_in_flight: %u tx.lost: %u tp->lost: %u rs->lost: %d "
|
|
|
|
+ "lost_prev: %d pcount: %d seq: %u end_seq: %u reneg: %u",
|
|
|
|
+ tcp_snd_cwnd(tp), inet_csk(sk)->icsk_ca_state,
|
|
|
|
+ tp->packets_out, tp->lost_out, tcp_packets_in_flight(tp),
|
|
|
|
+ rs->tx_in_flight, TCP_SKB_CB(skb)->tx.lost, tp->lost,
|
|
|
|
+ rs->lost, lost_prev, pcount,
|
|
|
|
+ TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
|
|
|
|
+ tp->is_sack_reneg))
|
|
|
|
+ return ~0U;
|
|
|
|
+
|
|
|
|
+ /* At what prefix of this lost skb did losss rate exceed loss_thresh? */
|
|
|
|
+ loss_budget = (u64)inflight_prev * loss_thresh + BBR_UNIT - 1;
|
|
|
|
+ loss_budget >>= BBR_SCALE;
|
|
|
|
+ if (lost_prev >= loss_budget) {
|
|
|
|
+ lost_prefix = 0; /* previous losses crossed loss_thresh */
|
|
|
|
+ } else {
|
|
|
|
+ lost_prefix = loss_budget - lost_prev;
|
|
|
|
+ lost_prefix <<= BBR_SCALE;
|
|
|
|
+ divisor = BBR_UNIT - loss_thresh;
|
|
|
|
+ if (WARN_ON_ONCE(!divisor)) /* loss_thresh is 8 bits */
|
|
|
|
+ return ~0U;
|
|
|
|
+ do_div(lost_prefix, divisor);
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ inflight_hi = inflight_prev + lost_prefix;
|
|
|
|
+ return inflight_hi;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* If loss/ECN rates during probing indicated we may have overfilled a
|
|
|
|
+ * buffer, return an operating point that tries to leave unutilized headroom in
|
|
|
|
+ * the path for other flows, for fairness convergence and lower RTTs and loss.
|
|
|
|
+ */
|
|
|
|
+static u32 bbr_inflight_with_headroom(const struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 headroom, headroom_fraction;
|
|
|
|
+
|
|
|
|
+ if (bbr->inflight_hi == ~0U)
|
|
|
|
+ return ~0U;
|
|
|
|
+
|
|
|
|
+ headroom_fraction = bbr_param(sk, inflight_headroom);
|
|
|
|
+ headroom = ((u64)bbr->inflight_hi * headroom_fraction) >> BBR_SCALE;
|
|
|
|
+ headroom = max(headroom, 1U);
|
|
|
|
+ return max_t(s32, bbr->inflight_hi - headroom,
|
|
|
|
+ bbr_param(sk, cwnd_min_target));
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Bound cwnd to a sensible level, based on our current probing state
|
|
|
|
+ * machine phase and model of a good inflight level (inflight_lo, inflight_hi).
|
|
|
|
+ */
|
|
|
|
+static void bbr_bound_cwnd_for_inflight_model(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 cap;
|
|
|
|
+
|
|
|
|
+ /* tcp_rcv_synsent_state_process() currently calls tcp_ack()
|
|
|
|
+ * and thus cong_control() without first initializing us(!).
|
|
|
|
+ */
|
|
|
|
+ if (!bbr->initialized)
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ cap = ~0U;
|
|
|
|
+ if (bbr->mode == BBR_PROBE_BW &&
|
|
|
|
+ bbr->cycle_idx != BBR_BW_PROBE_CRUISE) {
|
|
|
|
+ /* Probe to see if more packets fit in the path. */
|
|
|
|
+ cap = bbr->inflight_hi;
|
|
|
|
+ } else {
|
|
|
|
+ if (bbr->mode == BBR_PROBE_RTT ||
|
|
|
|
+ (bbr->mode == BBR_PROBE_BW &&
|
|
|
|
+ bbr->cycle_idx == BBR_BW_PROBE_CRUISE))
|
|
|
|
+ cap = bbr_inflight_with_headroom(sk);
|
|
|
|
+ }
|
|
|
|
+ /* Adapt to any loss/ECN since our last bw probe. */
|
|
|
|
+ cap = min(cap, bbr->inflight_lo);
|
|
|
|
+
|
|
|
|
+ cap = max_t(u32, cap, bbr_param(sk, cwnd_min_target));
|
|
|
|
+ tcp_snd_cwnd_set(tp, min(cap, tcp_snd_cwnd(tp)));
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* How should we multiplicatively cut bw or inflight limits based on ECN? */
|
|
|
|
+static u32 bbr_ecn_cut(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ return BBR_UNIT -
|
|
|
|
+ ((bbr->ecn_alpha * bbr_param(sk, ecn_factor)) >> BBR_SCALE);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Init lower bounds if have not inited yet. */
|
|
|
|
+static void bbr_init_lower_bounds(struct sock *sk, bool init_bw)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (init_bw && bbr->bw_lo == ~0U)
|
|
|
|
+ bbr->bw_lo = bbr_max_bw(sk);
|
|
|
|
+ if (bbr->inflight_lo == ~0U)
|
|
|
|
+ bbr->inflight_lo = tcp_snd_cwnd(tp);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Reduce bw and inflight to (1 - beta). */
|
|
|
|
+static void bbr_loss_lower_bounds(struct sock *sk, u32 *bw, u32 *inflight)
|
|
|
|
+{
|
|
|
|
+ struct bbr* bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 loss_cut = BBR_UNIT - bbr_param(sk, beta);
|
|
|
|
+
|
|
|
|
+ *bw = max_t(u32, bbr->bw_latest,
|
|
|
|
+ (u64)bbr->bw_lo * loss_cut >> BBR_SCALE);
|
|
|
|
+ *inflight = max_t(u32, bbr->inflight_latest,
|
|
|
|
+ (u64)bbr->inflight_lo * loss_cut >> BBR_SCALE);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Reduce inflight to (1 - alpha*ecn_factor). */
|
|
|
|
+static void bbr_ecn_lower_bounds(struct sock *sk, u32 *inflight)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 ecn_cut = bbr_ecn_cut(sk);
|
|
|
|
+
|
|
|
|
+ *inflight = (u64)bbr->inflight_lo * ecn_cut >> BBR_SCALE;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Estimate a short-term lower bound on the capacity available now, based
|
|
|
|
+ * on measurements of the current delivery process and recent history. When we
|
|
|
|
+ * are seeing loss/ECN at times when we are not probing bw, then conservatively
|
|
|
|
+ * move toward flow balance by multiplicatively cutting our short-term
|
|
|
|
+ * estimated safe rate and volume of data (bw_lo and inflight_lo). We use a
|
|
|
|
+ * multiplicative decrease in order to converge to a lower capacity in time
|
|
|
|
+ * logarithmic in the magnitude of the decrease.
|
|
|
|
+ *
|
|
|
|
+ * However, we do not cut our short-term estimates lower than the current rate
|
|
|
|
+ * and volume of delivered data from this round trip, since from the current
|
|
|
|
+ * delivery process we can estimate the measured capacity available now.
|
|
|
|
+ *
|
|
|
|
+ * Anything faster than that approach would knowingly risk high loss, which can
|
|
|
|
+ * cause low bw for Reno/CUBIC and high loss recovery latency for
|
|
|
|
+ * request/response flows using any congestion control.
|
|
|
|
+ */
|
|
|
|
+static void bbr_adapt_lower_bounds(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 ecn_inflight_lo = ~0U;
|
|
|
|
+
|
|
|
|
+ /* We only use lower-bound estimates when not probing bw.
|
|
|
|
+ * When probing we need to push inflight higher to probe bw.
|
|
|
|
+ */
|
|
|
|
+ if (bbr_is_probing_bandwidth(sk))
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ /* ECN response. */
|
|
|
|
+ if (bbr->ecn_in_round && bbr_param(sk, ecn_factor)) {
|
|
|
|
+ bbr_init_lower_bounds(sk, false);
|
|
|
|
+ bbr_ecn_lower_bounds(sk, &ecn_inflight_lo);
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ /* Loss response. */
|
|
|
|
+ if (bbr->loss_in_round) {
|
|
|
|
+ bbr_init_lower_bounds(sk, true);
|
|
|
|
+ bbr_loss_lower_bounds(sk, &bbr->bw_lo, &bbr->inflight_lo);
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ /* Adjust to the lower of the levels implied by loss/ECN. */
|
|
|
|
+ bbr->inflight_lo = min(bbr->inflight_lo, ecn_inflight_lo);
|
|
|
|
+ bbr->bw_lo = max(1U, bbr->bw_lo);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Reset any short-term lower-bound adaptation to congestion, so that we can
|
|
|
|
+ * push our inflight up.
|
|
|
|
+ */
|
|
|
|
+static void bbr_reset_lower_bounds(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->bw_lo = ~0U;
|
|
|
|
+ bbr->inflight_lo = ~0U;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* After bw probing (STARTUP/PROBE_UP), reset signals before entering a state
|
|
|
|
+ * machine phase where we adapt our lower bound based on congestion signals.
|
|
|
|
+ */
|
|
|
|
+static void bbr_reset_congestion_signals(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->loss_in_round = 0;
|
|
|
|
+ bbr->ecn_in_round = 0;
|
|
|
|
+ bbr->loss_in_cycle = 0;
|
|
|
|
+ bbr->ecn_in_cycle = 0;
|
|
|
|
+ bbr->bw_latest = 0;
|
|
|
|
+ bbr->inflight_latest = 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static void bbr_exit_loss_recovery(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp), bbr->prior_cwnd));
|
|
|
|
+ bbr->try_fast_path = 0; /* bound cwnd using latest model */
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Update rate and volume of delivered data from latest round trip. */
|
|
|
|
+static void bbr_update_latest_delivery_signals(
|
|
|
|
+ struct sock *sk, const struct rate_sample *rs, struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->loss_round_start = 0;
|
|
|
|
+ if (rs->interval_us <= 0 || !rs->acked_sacked)
|
|
|
|
+ return; /* Not a valid observation */
|
|
|
|
+
|
|
|
|
+ bbr->bw_latest = max_t(u32, bbr->bw_latest, ctx->sample_bw);
|
|
|
|
+ bbr->inflight_latest = max_t(u32, bbr->inflight_latest, rs->delivered);
|
|
|
|
+
|
|
|
|
+ if (!before(rs->prior_delivered, bbr->loss_round_delivered)) {
|
|
|
|
+ bbr->loss_round_delivered = tp->delivered;
|
|
|
|
+ bbr->loss_round_start = 1; /* mark start of new round trip */
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Once per round, reset filter for latest rate and volume of delivered data. */
|
|
|
|
+static void bbr_advance_latest_delivery_signals(
|
|
|
|
+ struct sock *sk, const struct rate_sample *rs, struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ /* If ACK matches a TLP retransmit, persist the filter. If we detect
|
|
|
|
+ * that a TLP retransmit plugged a tail loss, we'll want to remember
|
|
|
|
+ * how much data the path delivered before the tail loss.
|
|
|
|
+ */
|
|
|
|
+ if (bbr->loss_round_start && !rs->is_acking_tlp_retrans_seq) {
|
|
|
|
+ bbr->bw_latest = ctx->sample_bw;
|
|
|
|
+ bbr->inflight_latest = rs->delivered;
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Update (most of) our congestion signals: track the recent rate and volume of
|
|
|
|
+ * delivered data, presence of loss, and EWMA degree of ECN marking.
|
|
|
|
+ */
|
|
|
|
+static void bbr_update_congestion_signals(
|
|
|
|
+ struct sock *sk, const struct rate_sample *rs, struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u64 bw;
|
|
|
|
+
|
|
|
|
+ if (rs->interval_us <= 0 || !rs->acked_sacked)
|
|
|
|
+ return; /* Not a valid observation */
|
|
|
|
+ bw = ctx->sample_bw;
|
|
|
|
+
|
|
|
|
+ if (!rs->is_app_limited || bw >= bbr_max_bw(sk))
|
|
|
|
+ bbr_take_max_bw_sample(sk, bw);
|
|
|
|
+
|
|
|
|
+ bbr->loss_in_round |= (rs->losses > 0);
|
|
|
|
+
|
|
|
|
+ if (!bbr->loss_round_start)
|
|
|
|
+ return; /* skip the per-round-trip updates */
|
|
|
|
+ /* Now do per-round-trip updates. */
|
|
|
|
+ bbr_adapt_lower_bounds(sk, rs);
|
|
|
|
+
|
|
|
|
+ bbr->loss_in_round = 0;
|
|
|
|
+ bbr->ecn_in_round = 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Bandwidth probing can cause loss. To help coexistence with loss-based
|
|
|
|
+ * congestion control we spread out our probing in a Reno-conscious way. Due to
|
|
|
|
+ * the shape of the Reno sawtooth, the time required between loss epochs for an
|
|
|
|
+ * idealized Reno flow is a number of round trips that is the BDP of that
|
|
|
|
+ * flow. We count packet-timed round trips directly, since measured RTT can
|
|
|
|
+ * vary widely, and Reno is driven by packet-timed round trips.
|
|
|
|
+ */
|
|
|
|
+static bool bbr_is_reno_coexistence_probe_time(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 rounds;
|
|
|
|
+
|
|
|
|
+ /* Random loss can shave some small percentage off of our inflight
|
|
|
|
+ * in each round. To survive this, flows need robust periodic probes.
|
|
|
|
+ */
|
|
|
|
+ rounds = min_t(u32, bbr_param(sk, bw_probe_max_rounds), bbr_target_inflight(sk));
|
|
|
|
+ return bbr->rounds_since_probe >= rounds;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* How long do we want to wait before probing for bandwidth (and risking
|
|
|
|
+ * loss)? We randomize the wait, for better mixing and fairness convergence.
|
|
|
|
+ *
|
|
|
|
+ * We bound the Reno-coexistence inter-bw-probe time to be 62-63 round trips.
|
|
|
|
+ * This is calculated to allow fairness with a 25Mbps, 30ms Reno flow,
|
|
|
|
+ * (eg 4K video to a broadband user):
|
|
|
|
+ * BDP = 25Mbps * .030sec /(1514bytes) = 61.9 packets
|
|
|
|
+ *
|
|
|
|
+ * We bound the BBR-native inter-bw-probe wall clock time to be:
|
|
|
|
+ * (a) higher than 2 sec: to try to avoid causing loss for a long enough time
|
|
|
|
+ * to allow Reno at 30ms to get 4K video bw, the inter-bw-probe time must
|
|
|
|
+ * be at least: 25Mbps * .030sec / (1514bytes) * 0.030sec = 1.9secs
|
|
|
|
+ * (b) lower than 3 sec: to ensure flows can start probing in a reasonable
|
|
|
|
+ * amount of time to discover unutilized bw on human-scale interactive
|
|
|
|
+ * time-scales (e.g. perhaps traffic from a web page download that we
|
|
|
|
+ * were competing with is now complete).
|
|
|
|
+ */
|
|
|
|
+static void bbr_pick_probe_wait(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ /* Decide the random round-trip bound for wait until probe: */
|
|
|
|
+ bbr->rounds_since_probe =
|
|
|
|
+ get_random_u32_below(bbr_param(sk, bw_probe_rand_rounds));
|
|
|
|
+ /* Decide the random wall clock bound for wait until probe: */
|
|
|
|
+ bbr->probe_wait_us = bbr_param(sk, bw_probe_base_us) +
|
|
|
|
+ get_random_u32_below(bbr_param(sk, bw_probe_rand_us));
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static void bbr_set_cycle_idx(struct sock *sk, int cycle_idx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->cycle_idx = cycle_idx;
|
|
|
|
+ /* New phase, so need to update cwnd and pacing rate. */
|
|
|
|
+ bbr->try_fast_path = 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Send at estimated bw to fill the pipe, but not queue. We need this phase
|
|
|
|
+ * before PROBE_UP, because as soon as we send faster than the available bw
|
|
|
|
+ * we will start building a queue, and if the buffer is shallow we can cause
|
|
|
|
+ * loss. If we do not fill the pipe before we cause this loss, our bw_hi and
|
|
|
|
+ * inflight_hi estimates will underestimate.
|
|
|
|
+ */
|
|
|
|
+static void bbr_start_bw_probe_refill(struct sock *sk, u32 bw_probe_up_rounds)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr_reset_lower_bounds(sk);
|
|
|
|
+ bbr->bw_probe_up_rounds = bw_probe_up_rounds;
|
|
|
|
+ bbr->bw_probe_up_acks = 0;
|
|
|
|
+ bbr->stopped_risky_probe = 0;
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_REFILLING;
|
|
|
|
+ bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_REFILL);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Now probe max deliverable data rate and volume. */
|
|
|
|
+static void bbr_start_bw_probe_up(struct sock *sk, struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_PROBE_STARTING;
|
|
|
|
+ bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
+ bbr->cycle_mstamp = tp->tcp_mstamp;
|
|
|
|
+ bbr_reset_full_bw(sk);
|
|
|
|
+ bbr->full_bw = ctx->sample_bw;
|
|
|
|
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_UP);
|
|
|
|
+ bbr_raise_inflight_hi_slope(sk);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Start a new PROBE_BW probing cycle of some wall clock length. Pick a wall
|
|
|
|
+ * clock time at which to probe beyond an inflight that we think to be
|
|
|
|
+ * safe. This will knowingly risk packet loss, so we want to do this rarely, to
|
|
|
|
+ * keep packet loss rates low. Also start a round-trip counter, to probe faster
|
|
|
|
+ * if we estimate a Reno flow at our BDP would probe faster.
|
|
|
|
+ */
|
|
|
|
+static void bbr_start_bw_probe_down(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr_reset_congestion_signals(sk);
|
|
|
|
+ bbr->bw_probe_up_cnt = ~0U; /* not growing inflight_hi any more */
|
|
|
|
+ bbr_pick_probe_wait(sk);
|
|
|
|
+ bbr->cycle_mstamp = tp->tcp_mstamp; /* start wall clock */
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_PROBE_STOPPING;
|
|
|
|
+ bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_DOWN);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Cruise: maintain what we estimate to be a neutral, conservative
|
|
|
|
+ * operating point, without attempting to probe up for bandwidth or down for
|
|
|
|
+ * RTT, and only reducing inflight in response to loss/ECN signals.
|
|
|
|
+ */
|
|
|
|
+static void bbr_start_bw_probe_cruise(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (bbr->inflight_lo != ~0U)
|
|
|
|
+ bbr->inflight_lo = min(bbr->inflight_lo, bbr->inflight_hi);
|
|
|
|
+
|
|
|
|
+ bbr_set_cycle_idx(sk, BBR_BW_PROBE_CRUISE);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Loss and/or ECN rate is too high while probing.
|
|
|
|
+ * Adapt (once per bw probe) by cutting inflight_hi and then restarting cycle.
|
|
|
|
+ */
|
|
|
|
+static void bbr_handle_inflight_too_high(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ const u32 beta = bbr_param(sk, beta);
|
|
|
|
+
|
|
|
|
+ bbr->prev_probe_too_high = 1;
|
|
|
|
+ bbr->bw_probe_samples = 0; /* only react once per probe */
|
|
|
|
+ /* If we are app-limited then we are not robustly
|
|
|
|
+ * probing the max volume of inflight data we think
|
|
|
|
+ * might be safe (analogous to how app-limited bw
|
|
|
|
+ * samples are not known to be robustly probing bw).
|
|
|
|
+ */
|
|
|
|
+ if (!rs->is_app_limited) {
|
|
|
|
+ bbr->inflight_hi = max_t(u32, rs->tx_in_flight,
|
|
|
|
+ (u64)bbr_target_inflight(sk) *
|
|
|
|
+ (BBR_UNIT - beta) >> BBR_SCALE);
|
|
|
|
+ }
|
|
|
|
+ if (bbr->mode == BBR_PROBE_BW && bbr->cycle_idx == BBR_BW_PROBE_UP)
|
|
|
|
+ bbr_start_bw_probe_down(sk);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* If we're seeing bw and loss samples reflecting our bw probing, adapt
|
|
|
|
+ * using the signals we see. If loss or ECN mark rate gets too high, then adapt
|
|
|
|
+ * inflight_hi downward. If we're able to push inflight higher without such
|
|
|
|
+ * signals, push higher: adapt inflight_hi upward.
|
|
|
|
+ */
|
|
|
|
+static bool bbr_adapt_upper_bounds(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs,
|
|
|
|
+ struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ /* Track when we'll see bw/loss samples resulting from our bw probes. */
|
|
|
|
+ if (bbr->ack_phase == BBR_ACKS_PROBE_STARTING && bbr->round_start)
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_PROBE_FEEDBACK;
|
|
|
|
+ if (bbr->ack_phase == BBR_ACKS_PROBE_STOPPING && bbr->round_start) {
|
|
|
|
+ /* End of samples from bw probing phase. */
|
|
|
|
+ bbr->bw_probe_samples = 0;
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_INIT;
|
|
|
|
+ /* At this point in the cycle, our current bw sample is also
|
|
|
|
+ * our best recent chance at finding the highest available bw
|
|
|
|
+ * for this flow. So now is the best time to forget the bw
|
|
|
|
+ * samples from the previous cycle, by advancing the window.
|
|
|
|
+ */
|
|
|
|
+ if (bbr->mode == BBR_PROBE_BW && !rs->is_app_limited)
|
|
|
|
+ bbr_advance_max_bw_filter(sk);
|
|
|
|
+ /* If we had an inflight_hi, then probed and pushed inflight all
|
|
|
|
+ * the way up to hit that inflight_hi without seeing any
|
|
|
|
+ * high loss/ECN in all the resulting ACKs from that probing,
|
|
|
|
+ * then probe up again, this time letting inflight persist at
|
|
|
|
+ * inflight_hi for a round trip, then accelerating beyond.
|
|
|
|
+ */
|
|
|
|
+ if (bbr->mode == BBR_PROBE_BW &&
|
|
|
|
+ bbr->stopped_risky_probe && !bbr->prev_probe_too_high) {
|
|
|
|
+ bbr_start_bw_probe_refill(sk, 0);
|
|
|
|
+ return true; /* yes, decided state transition */
|
|
|
|
+ }
|
|
|
|
+ }
|
|
|
|
+ if (bbr_is_inflight_too_high(sk, rs)) {
|
|
|
|
+ if (bbr->bw_probe_samples) /* sample is from bw probing? */
|
|
|
|
+ bbr_handle_inflight_too_high(sk, rs);
|
|
|
|
+ } else {
|
|
|
|
+ /* Loss/ECN rate is declared safe. Adjust upper bound upward. */
|
|
|
|
+
|
|
|
|
+ if (bbr->inflight_hi == ~0U)
|
|
|
|
+ return false; /* no excess queue signals yet */
|
|
|
|
+
|
|
|
|
+ /* To be resilient to random loss, we must raise bw/inflight_hi
|
|
|
|
+ * if we observe in any phase that a higher level is safe.
|
|
|
|
+ */
|
|
|
|
+ if (rs->tx_in_flight > bbr->inflight_hi) {
|
|
|
|
+ bbr->inflight_hi = rs->tx_in_flight;
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ if (bbr->mode == BBR_PROBE_BW &&
|
|
|
|
+ bbr->cycle_idx == BBR_BW_PROBE_UP)
|
|
|
|
+ bbr_probe_inflight_hi_upward(sk, rs);
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ return false;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Check if it's time to probe for bandwidth now, and if so, kick it off. */
|
|
|
|
+static bool bbr_check_time_to_probe_bw(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 n;
|
|
|
|
+
|
|
|
|
+ /* If we seem to be at an operating point where we are not seeing loss
|
|
|
|
+ * but we are seeing ECN marks, then when the ECN marks cease we reprobe
|
|
|
|
+ * quickly (in case cross-traffic has ceased and freed up bw).
|
|
|
|
+ */
|
|
|
|
+ if (bbr_param(sk, ecn_reprobe_gain) && bbr->ecn_eligible &&
|
|
|
|
+ bbr->ecn_in_cycle && !bbr->loss_in_cycle &&
|
|
|
|
+ inet_csk(sk)->icsk_ca_state == TCP_CA_Open) {
|
|
|
|
+ /* Calculate n so that when bbr_raise_inflight_hi_slope()
|
|
|
|
+ * computes growth_this_round as 2^n it will be roughly the
|
|
|
|
+ * desired volume of data (inflight_hi*ecn_reprobe_gain).
|
|
|
|
+ */
|
|
|
|
+ n = ilog2((((u64)bbr->inflight_hi *
|
|
|
|
+ bbr_param(sk, ecn_reprobe_gain)) >> BBR_SCALE));
|
|
|
|
+ bbr_start_bw_probe_refill(sk, n);
|
|
|
|
+ return true;
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ if (bbr_has_elapsed_in_phase(sk, bbr->probe_wait_us) ||
|
|
|
|
+ bbr_is_reno_coexistence_probe_time(sk)) {
|
|
|
|
+ bbr_start_bw_probe_refill(sk, 0);
|
|
|
|
+ return true;
|
|
|
|
+ }
|
|
|
|
+ return false;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Is it time to transition from PROBE_DOWN to PROBE_CRUISE? */
|
|
|
|
+static bool bbr_check_time_to_cruise(struct sock *sk, u32 inflight, u32 bw)
|
|
|
|
+{
|
|
|
|
+ /* Always need to pull inflight down to leave headroom in queue. */
|
|
|
|
+ if (inflight > bbr_inflight_with_headroom(sk))
|
|
|
|
+ return false;
|
|
|
|
+
|
|
|
|
+ return inflight <= bbr_inflight(sk, bw, BBR_UNIT);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* PROBE_BW state machine: cruise, refill, probe for bw, or drain? */
|
|
|
|
+static void bbr_update_cycle_phase(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs,
|
|
|
|
+ struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ bool is_bw_probe_done = false;
|
|
|
|
+ u32 inflight, bw;
|
|
|
|
+
|
|
|
|
+ if (!bbr_full_bw_reached(sk))
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ /* In DRAIN, PROBE_BW, or PROBE_RTT, adjust upper bounds. */
|
|
|
|
+ if (bbr_adapt_upper_bounds(sk, rs, ctx))
|
|
|
|
+ return; /* already decided state transition */
|
|
|
|
+
|
|
|
|
+ if (bbr->mode != BBR_PROBE_BW)
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ inflight = bbr_packets_in_net_at_edt(sk, rs->prior_in_flight);
|
|
|
|
+ bw = bbr_max_bw(sk);
|
|
|
|
+
|
|
|
|
+ switch (bbr->cycle_idx) {
|
|
|
|
+ /* First we spend most of our time cruising with a pacing_gain of 1.0,
|
|
|
|
+ * which paces at the estimated bw, to try to fully use the pipe
|
|
|
|
+ * without building queue. If we encounter loss/ECN marks, we adapt
|
|
|
|
+ * by slowing down.
|
|
|
|
+ */
|
|
|
|
+ case BBR_BW_PROBE_CRUISE:
|
|
|
|
+ if (bbr_check_time_to_probe_bw(sk, rs))
|
|
|
|
+ return; /* already decided state transition */
|
|
|
|
+ break;
|
|
|
|
+
|
|
|
|
+ /* After cruising, when it's time to probe, we first "refill": we send
|
|
|
|
+ * at the estimated bw to fill the pipe, before probing higher and
|
|
|
|
+ * knowingly risking overflowing the bottleneck buffer (causing loss).
|
|
|
|
+ */
|
|
|
|
+ case BBR_BW_PROBE_REFILL:
|
|
|
|
+ if (bbr->round_start) {
|
|
|
|
+ /* After one full round trip of sending in REFILL, we
|
|
|
|
+ * start to see bw samples reflecting our REFILL, which
|
|
|
|
+ * may be putting too much data in flight.
|
|
|
|
+ */
|
|
|
|
+ bbr->bw_probe_samples = 1;
|
|
|
|
+ bbr_start_bw_probe_up(sk, ctx);
|
|
|
|
+ }
|
|
|
|
+ break;
|
|
|
|
+
|
|
|
|
+ /* After we refill the pipe, we probe by using a pacing_gain > 1.0, to
|
|
|
|
+ * probe for bw. If we have not seen loss/ECN, we try to raise inflight
|
|
|
|
+ * to at least pacing_gain*BDP; note that this may take more than
|
|
|
|
+ * min_rtt if min_rtt is small (e.g. on a LAN).
|
|
|
|
+ *
|
|
|
|
+ * We terminate PROBE_UP bandwidth probing upon any of the following:
|
|
|
|
+ *
|
|
|
|
+ * (1) We've pushed inflight up to hit the inflight_hi target set in the
|
|
|
|
+ * most recent previous bw probe phase. Thus we want to start
|
|
|
|
+ * draining the queue immediately because it's very likely the most
|
|
|
|
+ * recently sent packets will fill the queue and cause drops.
|
|
|
|
+ * (2) If inflight_hi has not limited bandwidth growth recently, and
|
|
|
|
+ * yet delivered bandwidth has not increased much recently
|
|
|
|
+ * (bbr->full_bw_now).
|
|
|
|
+ * (3) Loss filter says loss rate is "too high".
|
|
|
|
+ * (4) ECN filter says ECN mark rate is "too high".
|
|
|
|
+ *
|
|
|
|
+ * (1) (2) checked here, (3) (4) checked in bbr_is_inflight_too_high()
|
|
|
|
+ */
|
|
|
|
+ case BBR_BW_PROBE_UP:
|
|
|
|
+ if (bbr->prev_probe_too_high &&
|
|
|
|
+ inflight >= bbr->inflight_hi) {
|
|
|
|
+ bbr->stopped_risky_probe = 1;
|
|
|
|
+ is_bw_probe_done = true;
|
|
|
|
+ } else {
|
|
|
|
+ if (tp->is_cwnd_limited &&
|
|
|
|
+ tcp_snd_cwnd(tp) >= bbr->inflight_hi) {
|
|
|
|
+ /* inflight_hi is limiting bw growth */
|
|
|
|
+ bbr_reset_full_bw(sk);
|
|
|
|
+ bbr->full_bw = ctx->sample_bw;
|
|
|
|
+ } else if (bbr->full_bw_now) {
|
|
|
|
+ /* Plateau in estimated bw. Pipe looks full. */
|
|
|
|
+ is_bw_probe_done = true;
|
|
|
|
+ }
|
|
|
|
+ }
|
|
|
|
+ if (is_bw_probe_done) {
|
|
|
|
+ bbr->prev_probe_too_high = 0; /* no loss/ECN (yet) */
|
|
|
|
+ bbr_start_bw_probe_down(sk); /* restart w/ down */
|
|
|
|
+ }
|
|
|
|
+ break;
|
|
|
|
+
|
|
|
|
+ /* After probing in PROBE_UP, we have usually accumulated some data in
|
|
|
|
+ * the bottleneck buffer (if bw probing didn't find more bw). We next
|
|
|
|
+ * enter PROBE_DOWN to try to drain any excess data from the queue. To
|
|
|
|
+ * do this, we use a pacing_gain < 1.0. We hold this pacing gain until
|
|
|
|
+ * our inflight is less then that target cruising point, which is the
|
|
|
|
+ * minimum of (a) the amount needed to leave headroom, and (b) the
|
|
|
|
+ * estimated BDP. Once inflight falls to match the target, we estimate
|
|
|
|
+ * the queue is drained; persisting would underutilize the pipe.
|
|
|
|
+ */
|
|
|
|
+ case BBR_BW_PROBE_DOWN:
|
|
|
|
+ if (bbr_check_time_to_probe_bw(sk, rs))
|
|
|
|
+ return; /* already decided state transition */
|
|
|
|
+ if (bbr_check_time_to_cruise(sk, inflight, bw))
|
|
|
|
+ bbr_start_bw_probe_cruise(sk);
|
|
|
|
+ break;
|
|
|
|
+
|
|
|
|
+ default:
|
|
|
|
+ WARN_ONCE(1, "BBR invalid cycle index %u\n", bbr->cycle_idx);
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Exiting PROBE_RTT, so return to bandwidth probing in STARTUP or PROBE_BW. */
|
|
|
|
+static void bbr_exit_probe_rtt(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ bbr_reset_lower_bounds(sk);
|
|
|
|
+ if (bbr_full_bw_reached(sk)) {
|
|
|
|
+ bbr->mode = BBR_PROBE_BW;
|
|
|
|
+ /* Raising inflight after PROBE_RTT may cause loss, so reset
|
|
|
|
+ * the PROBE_BW clock and schedule the next bandwidth probe for
|
|
|
|
+ * a friendly and randomized future point in time.
|
|
|
|
+ */
|
|
|
|
+ bbr_start_bw_probe_down(sk);
|
|
|
|
+ /* Since we are exiting PROBE_RTT, we know inflight is
|
|
|
|
+ * below our estimated BDP, so it is reasonable to cruise.
|
|
|
|
+ */
|
|
|
|
+ bbr_start_bw_probe_cruise(sk);
|
|
|
|
+ } else {
|
|
|
|
+ bbr->mode = BBR_STARTUP;
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Exit STARTUP based on loss rate > 1% and loss gaps in round >= N. Wait until
|
|
|
|
+ * the end of the round in recovery to get a good estimate of how many packets
|
|
|
|
+ * have been lost, and how many we need to drain with a low pacing rate.
|
|
|
|
+ */
|
|
|
|
+static void bbr_check_loss_too_high_in_startup(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (bbr_full_bw_reached(sk))
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ /* For STARTUP exit, check the loss rate at the end of each round trip
|
|
|
|
+ * of Recovery episodes in STARTUP. We check the loss rate at the end
|
|
|
|
+ * of the round trip to filter out noisy/low loss and have a better
|
|
|
|
+ * sense of inflight (extent of loss), so we can drain more accurately.
|
|
|
|
+ */
|
|
|
|
+ if (rs->losses && bbr->loss_events_in_round < 0xf)
|
|
|
|
+ bbr->loss_events_in_round++; /* update saturating counter */
|
|
|
|
+ if (bbr_param(sk, full_loss_cnt) && bbr->loss_round_start &&
|
|
|
|
+ inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery &&
|
|
|
|
+ bbr->loss_events_in_round >= bbr_param(sk, full_loss_cnt) &&
|
|
|
|
+ bbr_is_inflight_too_high(sk, rs)) {
|
|
|
|
+ bbr_handle_queue_too_high_in_startup(sk);
|
|
|
|
+ return;
|
|
|
|
+ }
|
|
|
|
+ if (bbr->loss_round_start)
|
|
|
|
+ bbr->loss_events_in_round = 0;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Estimate when the pipe is full, using the change in delivery rate: BBR
|
|
|
|
+ * estimates bw probing filled the pipe if the estimated bw hasn't changed by
|
|
|
|
+ * at least bbr_full_bw_thresh (25%) after bbr_full_bw_cnt (3) non-app-limited
|
|
|
|
+ * rounds. Why 3 rounds: 1: rwin autotuning grows the rwin, 2: we fill the
|
|
|
|
+ * higher rwin, 3: we get higher delivery rate samples. Or transient
|
|
|
|
+ * cross-traffic or radio noise can go away. CUBIC Hystart shares a similar
|
|
|
|
+ * design goal, but uses delay and inter-ACK spacing instead of bandwidth.
|
|
|
|
+ */
|
|
|
|
+static void bbr_check_full_bw_reached(struct sock *sk,
|
|
|
|
+ const struct rate_sample *rs,
|
|
|
|
+ struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 bw_thresh, full_cnt, thresh;
|
|
|
|
+
|
|
|
|
+ if (bbr->full_bw_now || rs->is_app_limited)
|
|
|
|
+ return;
|
|
|
|
+
|
|
|
|
+ thresh = bbr_param(sk, full_bw_thresh);
|
|
|
|
+ full_cnt = bbr_param(sk, full_bw_cnt);
|
|
|
|
+ bw_thresh = (u64)bbr->full_bw * thresh >> BBR_SCALE;
|
|
|
|
+ if (ctx->sample_bw >= bw_thresh) {
|
|
|
|
+ bbr_reset_full_bw(sk);
|
|
|
|
+ bbr->full_bw = ctx->sample_bw;
|
|
|
|
+ return;
|
|
|
|
+ }
|
|
|
|
+ if (!bbr->round_start)
|
|
|
|
+ return;
|
|
|
|
+ ++bbr->full_bw_cnt;
|
|
|
|
+ bbr->full_bw_now = bbr->full_bw_cnt >= full_cnt;
|
|
|
|
+ bbr->full_bw_reached |= bbr->full_bw_now;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* If pipe is probably full, drain the queue and then enter steady-state. */
|
|
|
|
+static void bbr_check_drain(struct sock *sk, const struct rate_sample *rs,
|
|
|
|
+ struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ if (bbr->mode == BBR_STARTUP && bbr_full_bw_reached(sk)) {
|
|
|
|
+ bbr->mode = BBR_DRAIN; /* drain queue we created */
|
|
|
|
+ /* Set ssthresh to export purely for monitoring, to signal
|
|
|
|
+ * completion of initial STARTUP by setting to a non-
|
|
|
|
+ * TCP_INFINITE_SSTHRESH value (ssthresh is not used by BBR).
|
|
|
|
+ */
|
|
|
|
+ tcp_sk(sk)->snd_ssthresh =
|
|
|
|
+ bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT);
|
|
|
|
+ bbr_reset_congestion_signals(sk);
|
|
|
|
+ } /* fall through to check if in-flight is already small: */
|
|
|
|
+ if (bbr->mode == BBR_DRAIN &&
|
|
|
|
+ bbr_packets_in_net_at_edt(sk, tcp_packets_in_flight(tcp_sk(sk))) <=
|
|
|
|
+ bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT)) {
|
|
|
|
+ bbr->mode = BBR_PROBE_BW;
|
|
|
|
+ bbr_start_bw_probe_down(sk);
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static void bbr_update_model(struct sock *sk, const struct rate_sample *rs,
|
|
|
|
+ struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ bbr_update_congestion_signals(sk, rs, ctx);
|
|
|
|
bbr_update_ack_aggregation(sk, rs);
|
|
|
|
- bbr_update_cycle_phase(sk, rs);
|
|
|
|
- bbr_check_full_bw_reached(sk, rs);
|
|
|
|
- bbr_check_drain(sk, rs);
|
|
|
|
+ bbr_check_loss_too_high_in_startup(sk, rs);
|
|
|
|
+ bbr_check_full_bw_reached(sk, rs, ctx);
|
|
|
|
+ bbr_check_drain(sk, rs, ctx);
|
|
|
|
+ bbr_update_cycle_phase(sk, rs, ctx);
|
|
|
|
bbr_update_min_rtt(sk, rs);
|
|
|
|
- bbr_update_gains(sk);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Fast path for app-limited case.
|
|
|
|
+ *
|
|
|
|
+ * On each ack, we execute bbr state machine, which primarily consists of:
|
|
|
|
+ * 1) update model based on new rate sample, and
|
|
|
|
+ * 2) update control based on updated model or state change.
|
|
|
|
+ *
|
|
|
|
+ * There are certain workload/scenarios, e.g. app-limited case, where
|
|
|
|
+ * either we can skip updating model or we can skip update of both model
|
|
|
|
+ * as well as control. This provides signifcant softirq cpu savings for
|
|
|
|
+ * processing incoming acks.
|
|
|
|
+ *
|
|
|
|
+ * In case of app-limited, if there is no congestion (loss/ecn) and
|
|
|
|
+ * if observed bw sample is less than current estimated bw, then we can
|
|
|
|
+ * skip some of the computation in bbr state processing:
|
|
|
|
+ *
|
|
|
|
+ * - if there is no rtt/mode/phase change: In this case, since all the
|
|
|
|
+ * parameters of the network model are constant, we can skip model
|
|
|
|
+ * as well control update.
|
|
|
|
+ *
|
|
|
|
+ * - else we can skip rest of the model update. But we still need to
|
|
|
|
+ * update the control to account for the new rtt/mode/phase.
|
|
|
|
+ *
|
|
|
|
+ * Returns whether we can take fast path or not.
|
|
|
|
+ */
|
|
|
|
+static bool bbr_run_fast_path(struct sock *sk, bool *update_model,
|
|
|
|
+ const struct rate_sample *rs, struct bbr_context *ctx)
|
|
|
|
+{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ u32 prev_min_rtt_us, prev_mode;
|
|
|
|
+
|
|
|
|
+ if (bbr_param(sk, fast_path) && bbr->try_fast_path &&
|
|
|
|
+ rs->is_app_limited && ctx->sample_bw < bbr_max_bw(sk) &&
|
|
|
|
+ !bbr->loss_in_round && !bbr->ecn_in_round ) {
|
|
|
|
+ prev_mode = bbr->mode;
|
|
|
|
+ prev_min_rtt_us = bbr->min_rtt_us;
|
|
|
|
+ bbr_check_drain(sk, rs, ctx);
|
|
|
|
+ bbr_update_cycle_phase(sk, rs, ctx);
|
|
|
|
+ bbr_update_min_rtt(sk, rs);
|
|
|
|
+
|
|
|
|
+ if (bbr->mode == prev_mode &&
|
|
|
|
+ bbr->min_rtt_us == prev_min_rtt_us &&
|
|
|
|
+ bbr->try_fast_path) {
|
|
|
|
+ return true;
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ /* Skip model update, but control still needs to be updated */
|
|
|
|
+ *update_model = false;
|
|
|
|
+ }
|
|
|
|
+ return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
__bpf_kfunc static void bbr_main(struct sock *sk, u32 ack, int flag, const struct rate_sample *rs)
|
|
|
|
{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u32 bw;
|
|
|
|
+ struct bbr_context ctx = { 0 };
|
|
|
|
+ bool update_model = true;
|
|
|
|
+ u32 bw, round_delivered;
|
|
|
|
+ int ce_ratio = -1;
|
|
|
|
+
|
|
|
|
+ round_delivered = bbr_update_round_start(sk, rs, &ctx);
|
|
|
|
+ if (bbr->round_start) {
|
|
|
|
+ bbr->rounds_since_probe =
|
|
|
|
+ min_t(s32, bbr->rounds_since_probe + 1, 0xFF);
|
|
|
|
+ ce_ratio = bbr_update_ecn_alpha(sk);
|
|
|
|
+ }
|
|
|
|
+ bbr_plb(sk, rs, ce_ratio);
|
|
|
|
+
|
|
|
|
+ bbr->ecn_in_round |= (bbr->ecn_eligible && rs->is_ece);
|
|
|
|
+ bbr_calculate_bw_sample(sk, rs, &ctx);
|
|
|
|
+ bbr_update_latest_delivery_signals(sk, rs, &ctx);
|
|
|
|
|
|
|
|
- bbr_update_model(sk, rs);
|
|
|
|
+ if (bbr_run_fast_path(sk, &update_model, rs, &ctx))
|
|
|
|
+ goto out;
|
|
|
|
|
|
|
|
+ if (update_model)
|
|
|
|
+ bbr_update_model(sk, rs, &ctx);
|
|
|
|
+
|
|
|
|
+ bbr_update_gains(sk);
|
|
|
|
bw = bbr_bw(sk);
|
|
|
|
bbr_set_pacing_rate(sk, bw, bbr->pacing_gain);
|
|
|
|
- bbr_set_cwnd(sk, rs, rs->acked_sacked, bw, bbr->cwnd_gain);
|
|
|
|
+ bbr_set_cwnd(sk, rs, rs->acked_sacked, bw, bbr->cwnd_gain,
|
|
|
|
+ tcp_snd_cwnd(tp), &ctx);
|
|
|
|
+ bbr_bound_cwnd_for_inflight_model(sk);
|
|
|
|
+
|
|
|
|
+out:
|
|
|
|
+ bbr_advance_latest_delivery_signals(sk, rs, &ctx);
|
|
|
|
+ bbr->prev_ca_state = inet_csk(sk)->icsk_ca_state;
|
|
|
|
+ bbr->loss_in_cycle |= rs->lost > 0;
|
|
|
|
+ bbr->ecn_in_cycle |= rs->delivered_ce > 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
__bpf_kfunc static void bbr_init(struct sock *sk)
|
|
|
|
@@ -1056,20 +2079,21 @@ __bpf_kfunc static void bbr_init(struct
|
|
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
|
|
|
|
- bbr->prior_cwnd = 0;
|
|
|
|
+ bbr->initialized = 1;
|
|
|
|
+
|
|
|
|
+ bbr->init_cwnd = min(0x7FU, tcp_snd_cwnd(tp));
|
|
|
|
+ bbr->prior_cwnd = tp->prior_cwnd;
|
|
|
|
tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
|
|
|
|
- bbr->rtt_cnt = 0;
|
|
|
|
bbr->next_rtt_delivered = tp->delivered;
|
|
|
|
bbr->prev_ca_state = TCP_CA_Open;
|
|
|
|
- bbr->packet_conservation = 0;
|
|
|
|
|
|
|
|
bbr->probe_rtt_done_stamp = 0;
|
|
|
|
bbr->probe_rtt_round_done = 0;
|
|
|
|
+ bbr->probe_rtt_min_us = tcp_min_rtt(tp);
|
|
|
|
+ bbr->probe_rtt_min_stamp = tcp_jiffies32;
|
|
|
|
bbr->min_rtt_us = tcp_min_rtt(tp);
|
|
|
|
bbr->min_rtt_stamp = tcp_jiffies32;
|
|
|
|
|
|
|
|
- minmax_reset(&bbr->bw, bbr->rtt_cnt, 0); /* init max bw to 0 */
|
|
|
|
-
|
|
|
|
bbr->has_seen_rtt = 0;
|
|
|
|
bbr_init_pacing_rate_from_rtt(sk);
|
|
|
|
|
|
|
|
@@ -1080,7 +2104,7 @@ __bpf_kfunc static void bbr_init(struct
|
|
|
|
bbr->full_bw_cnt = 0;
|
|
|
|
bbr->cycle_mstamp = 0;
|
|
|
|
bbr->cycle_idx = 0;
|
|
|
|
- bbr_reset_lt_bw_sampling(sk);
|
|
|
|
+
|
|
|
|
bbr_reset_startup_mode(sk);
|
|
|
|
|
|
|
|
bbr->ack_epoch_mstamp = tp->tcp_mstamp;
|
|
|
|
@@ -1090,78 +2114,236 @@ __bpf_kfunc static void bbr_init(struct
|
|
|
|
bbr->extra_acked[0] = 0;
|
|
|
|
bbr->extra_acked[1] = 0;
|
|
|
|
|
|
|
|
+ bbr->ce_state = 0;
|
|
|
|
+ bbr->prior_rcv_nxt = tp->rcv_nxt;
|
|
|
|
+ bbr->try_fast_path = 0;
|
|
|
|
+
|
|
|
|
cmpxchg(&sk->sk_pacing_status, SK_PACING_NONE, SK_PACING_NEEDED);
|
|
|
|
+
|
|
|
|
+ /* Start sampling ECN mark rate after first full flight is ACKed: */
|
|
|
|
+ bbr->loss_round_delivered = tp->delivered + 1;
|
|
|
|
+ bbr->loss_round_start = 0;
|
|
|
|
+ bbr->undo_bw_lo = 0;
|
|
|
|
+ bbr->undo_inflight_lo = 0;
|
|
|
|
+ bbr->undo_inflight_hi = 0;
|
|
|
|
+ bbr->loss_events_in_round = 0;
|
|
|
|
+ bbr->startup_ecn_rounds = 0;
|
|
|
|
+ bbr_reset_congestion_signals(sk);
|
|
|
|
+ bbr->bw_lo = ~0U;
|
|
|
|
+ bbr->bw_hi[0] = 0;
|
|
|
|
+ bbr->bw_hi[1] = 0;
|
|
|
|
+ bbr->inflight_lo = ~0U;
|
|
|
|
+ bbr->inflight_hi = ~0U;
|
|
|
|
+ bbr_reset_full_bw(sk);
|
|
|
|
+ bbr->bw_probe_up_cnt = ~0U;
|
|
|
|
+ bbr->bw_probe_up_acks = 0;
|
|
|
|
+ bbr->bw_probe_up_rounds = 0;
|
|
|
|
+ bbr->probe_wait_us = 0;
|
|
|
|
+ bbr->stopped_risky_probe = 0;
|
|
|
|
+ bbr->ack_phase = BBR_ACKS_INIT;
|
|
|
|
+ bbr->rounds_since_probe = 0;
|
|
|
|
+ bbr->bw_probe_samples = 0;
|
|
|
|
+ bbr->prev_probe_too_high = 0;
|
|
|
|
+ bbr->ecn_eligible = 0;
|
|
|
|
+ bbr->ecn_alpha = bbr_param(sk, ecn_alpha_init);
|
|
|
|
+ bbr->alpha_last_delivered = 0;
|
|
|
|
+ bbr->alpha_last_delivered_ce = 0;
|
|
|
|
+ bbr->plb.pause_until = 0;
|
|
|
|
+
|
|
|
|
+ tp->fast_ack_mode = bbr_fast_ack_mode ? 1 : 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
-__bpf_kfunc static u32 bbr_sndbuf_expand(struct sock *sk)
|
|
|
|
+/* BBR marks the current round trip as a loss round. */
|
|
|
|
+static void bbr_note_loss(struct sock *sk)
|
|
|
|
{
|
|
|
|
- /* Provision 3 * cwnd since BBR may slow-start even during recovery. */
|
|
|
|
- return 3;
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
+ /* Capture "current" data over the full round trip of loss, to
|
|
|
|
+ * have a better chance of observing the full capacity of the path.
|
|
|
|
+ */
|
|
|
|
+ if (!bbr->loss_in_round) /* first loss in this round trip? */
|
|
|
|
+ bbr->loss_round_delivered = tp->delivered; /* set round trip */
|
|
|
|
+ bbr->loss_in_round = 1;
|
|
|
|
+ bbr->loss_in_cycle = 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
-/* In theory BBR does not need to undo the cwnd since it does not
|
|
|
|
- * always reduce cwnd on losses (see bbr_main()). Keep it for now.
|
|
|
|
- */
|
|
|
|
+/* Core TCP stack informs us that the given skb was just marked lost. */
|
|
|
|
+__bpf_kfunc static void bbr_skb_marked_lost(struct sock *sk,
|
|
|
|
+ const struct sk_buff *skb)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
|
|
|
|
+ struct rate_sample rs = {};
|
|
|
|
+
|
|
|
|
+ bbr_note_loss(sk);
|
|
|
|
+
|
|
|
|
+ if (!bbr->bw_probe_samples)
|
|
|
|
+ return; /* not an skb sent while probing for bandwidth */
|
|
|
|
+ if (unlikely(!scb->tx.delivered_mstamp))
|
|
|
|
+ return; /* skb was SACKed, reneged, marked lost; ignore it */
|
|
|
|
+ /* We are probing for bandwidth. Construct a rate sample that
|
|
|
|
+ * estimates what happened in the flight leading up to this lost skb,
|
|
|
|
+ * then see if the loss rate went too high, and if so at which packet.
|
|
|
|
+ */
|
|
|
|
+ rs.tx_in_flight = scb->tx.in_flight;
|
|
|
|
+ rs.lost = tp->lost - scb->tx.lost;
|
|
|
|
+ rs.is_app_limited = scb->tx.is_app_limited;
|
|
|
|
+ if (bbr_is_inflight_too_high(sk, &rs)) {
|
|
|
|
+ rs.tx_in_flight = bbr_inflight_hi_from_lost_skb(sk, &rs, skb);
|
|
|
|
+ bbr_handle_inflight_too_high(sk, &rs);
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+static void bbr_run_loss_probe_recovery(struct sock *sk)
|
|
|
|
+{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+ struct rate_sample rs = {0};
|
|
|
|
+
|
|
|
|
+ bbr_note_loss(sk);
|
|
|
|
+
|
|
|
|
+ if (!bbr->bw_probe_samples)
|
|
|
|
+ return; /* not sent while probing for bandwidth */
|
|
|
|
+ /* We are probing for bandwidth. Construct a rate sample that
|
|
|
|
+ * estimates what happened in the flight leading up to this
|
|
|
|
+ * loss, then see if the loss rate went too high.
|
|
|
|
+ */
|
|
|
|
+ rs.lost = 1; /* TLP probe repaired loss of a single segment */
|
|
|
|
+ rs.tx_in_flight = bbr->inflight_latest + rs.lost;
|
|
|
|
+ rs.is_app_limited = tp->tlp_orig_data_app_limited;
|
|
|
|
+ if (bbr_is_inflight_too_high(sk, &rs))
|
|
|
|
+ bbr_handle_inflight_too_high(sk, &rs);
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+/* Revert short-term model if current loss recovery event was spurious. */
|
|
|
|
__bpf_kfunc static u32 bbr_undo_cwnd(struct sock *sk)
|
|
|
|
{
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
|
|
|
|
- bbr->full_bw = 0; /* spurious slow-down; reset full pipe detection */
|
|
|
|
- bbr->full_bw_cnt = 0;
|
|
|
|
- bbr_reset_lt_bw_sampling(sk);
|
|
|
|
- return tcp_snd_cwnd(tcp_sk(sk));
|
|
|
|
+ bbr_reset_full_bw(sk); /* spurious slow-down; reset full bw detector */
|
|
|
|
+ bbr->loss_in_round = 0;
|
|
|
|
+
|
|
|
|
+ /* Revert to cwnd and other state saved before loss episode. */
|
|
|
|
+ bbr->bw_lo = max(bbr->bw_lo, bbr->undo_bw_lo);
|
|
|
|
+ bbr->inflight_lo = max(bbr->inflight_lo, bbr->undo_inflight_lo);
|
|
|
|
+ bbr->inflight_hi = max(bbr->inflight_hi, bbr->undo_inflight_hi);
|
|
|
|
+ bbr->try_fast_path = 0; /* take slow path to set proper cwnd, pacing */
|
|
|
|
+ return bbr->prior_cwnd;
|
|
|
|
}
|
|
|
|
|
|
|
|
-/* Entering loss recovery, so save cwnd for when we exit or undo recovery. */
|
|
|
|
+/* Entering loss recovery, so save state for when we undo recovery. */
|
|
|
|
__bpf_kfunc static u32 bbr_ssthresh(struct sock *sk)
|
|
|
|
{
|
|
|
|
+ struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
+
|
|
|
|
bbr_save_cwnd(sk);
|
|
|
|
+ /* For undo, save state that adapts based on loss signal. */
|
|
|
|
+ bbr->undo_bw_lo = bbr->bw_lo;
|
|
|
|
+ bbr->undo_inflight_lo = bbr->inflight_lo;
|
|
|
|
+ bbr->undo_inflight_hi = bbr->inflight_hi;
|
|
|
|
return tcp_sk(sk)->snd_ssthresh;
|
|
|
|
}
|
|
|
|
|
|
|
|
+static enum tcp_bbr_phase bbr_get_phase(struct bbr *bbr)
|
|
|
|
+{
|
|
|
|
+ switch (bbr->mode) {
|
|
|
|
+ case BBR_STARTUP:
|
|
|
|
+ return BBR_PHASE_STARTUP;
|
|
|
|
+ case BBR_DRAIN:
|
|
|
|
+ return BBR_PHASE_DRAIN;
|
|
|
|
+ case BBR_PROBE_BW:
|
|
|
|
+ break;
|
|
|
|
+ case BBR_PROBE_RTT:
|
|
|
|
+ return BBR_PHASE_PROBE_RTT;
|
|
|
|
+ default:
|
|
|
|
+ return BBR_PHASE_INVALID;
|
|
|
|
+ }
|
|
|
|
+ switch (bbr->cycle_idx) {
|
|
|
|
+ case BBR_BW_PROBE_UP:
|
|
|
|
+ return BBR_PHASE_PROBE_BW_UP;
|
|
|
|
+ case BBR_BW_PROBE_DOWN:
|
|
|
|
+ return BBR_PHASE_PROBE_BW_DOWN;
|
|
|
|
+ case BBR_BW_PROBE_CRUISE:
|
|
|
|
+ return BBR_PHASE_PROBE_BW_CRUISE;
|
|
|
|
+ case BBR_BW_PROBE_REFILL:
|
|
|
|
+ return BBR_PHASE_PROBE_BW_REFILL;
|
|
|
|
+ default:
|
|
|
|
+ return BBR_PHASE_INVALID;
|
|
|
|
+ }
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
static size_t bbr_get_info(struct sock *sk, u32 ext, int *attr,
|
|
|
|
- union tcp_cc_info *info)
|
|
|
|
+ union tcp_cc_info *info)
|
|
|
|
{
|
|
|
|
if (ext & (1 << (INET_DIAG_BBRINFO - 1)) ||
|
|
|
|
ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
|
|
|
|
- struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
- u64 bw = bbr_bw(sk);
|
|
|
|
-
|
|
|
|
- bw = bw * tp->mss_cache * USEC_PER_SEC >> BW_SCALE;
|
|
|
|
- memset(&info->bbr, 0, sizeof(info->bbr));
|
|
|
|
- info->bbr.bbr_bw_lo = (u32)bw;
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|
|
|
- info->bbr.bbr_bw_hi = (u32)(bw >> 32);
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|
|
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- info->bbr.bbr_min_rtt = bbr->min_rtt_us;
|
|
|
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- info->bbr.bbr_pacing_gain = bbr->pacing_gain;
|
|
|
|
- info->bbr.bbr_cwnd_gain = bbr->cwnd_gain;
|
|
|
|
+ u64 bw = bbr_bw_bytes_per_sec(sk, bbr_bw(sk));
|
|
|
|
+ u64 bw_hi = bbr_bw_bytes_per_sec(sk, bbr_max_bw(sk));
|
|
|
|
+ u64 bw_lo = bbr->bw_lo == ~0U ?
|
|
|
|
+ ~0ULL : bbr_bw_bytes_per_sec(sk, bbr->bw_lo);
|
|
|
|
+ struct tcp_bbr_info *bbr_info = &info->bbr;
|
|
|
|
+
|
|
|
|
+ memset(bbr_info, 0, sizeof(*bbr_info));
|
|
|
|
+ bbr_info->bbr_bw_lo = (u32)bw;
|
|
|
|
+ bbr_info->bbr_bw_hi = (u32)(bw >> 32);
|
|
|
|
+ bbr_info->bbr_min_rtt = bbr->min_rtt_us;
|
|
|
|
+ bbr_info->bbr_pacing_gain = bbr->pacing_gain;
|
|
|
|
+ bbr_info->bbr_cwnd_gain = bbr->cwnd_gain;
|
|
|
|
+ bbr_info->bbr_bw_hi_lsb = (u32)bw_hi;
|
|
|
|
+ bbr_info->bbr_bw_hi_msb = (u32)(bw_hi >> 32);
|
|
|
|
+ bbr_info->bbr_bw_lo_lsb = (u32)bw_lo;
|
|
|
|
+ bbr_info->bbr_bw_lo_msb = (u32)(bw_lo >> 32);
|
|
|
|
+ bbr_info->bbr_mode = bbr->mode;
|
|
|
|
+ bbr_info->bbr_phase = (__u8)bbr_get_phase(bbr);
|
|
|
|
+ bbr_info->bbr_version = (__u8)BBR_VERSION;
|
|
|
|
+ bbr_info->bbr_inflight_lo = bbr->inflight_lo;
|
|
|
|
+ bbr_info->bbr_inflight_hi = bbr->inflight_hi;
|
|
|
|
+ bbr_info->bbr_extra_acked = bbr_extra_acked(sk);
|
|
|
|
*attr = INET_DIAG_BBRINFO;
|
|
|
|
- return sizeof(info->bbr);
|
|
|
|
+ return sizeof(*bbr_info);
|
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
__bpf_kfunc static void bbr_set_state(struct sock *sk, u8 new_state)
|
|
|
|
{
|
|
|
|
+ struct tcp_sock *tp = tcp_sk(sk);
|
|
|
|
struct bbr *bbr = inet_csk_ca(sk);
|
|
|
|
|
|
|
|
if (new_state == TCP_CA_Loss) {
|
|
|
|
- struct rate_sample rs = { .losses = 1 };
|
|
|
|
|
|
|
|
bbr->prev_ca_state = TCP_CA_Loss;
|
|
|
|
- bbr->full_bw = 0;
|
|
|
|
- bbr->round_start = 1; /* treat RTO like end of a round */
|
|
|
|
- bbr_lt_bw_sampling(sk, &rs);
|
|
|
|
+ tcp_plb_update_state_upon_rto(sk, &bbr->plb);
|
|
|
|
+ /* The tcp_write_timeout() call to sk_rethink_txhash() likely
|
|
|
|
+ * repathed this flow, so re-learn the min network RTT on the
|
|
|
|
+ * new path:
|
|
|
|
+ */
|
|
|
|
+ bbr_reset_full_bw(sk);
|
|
|
|
+ if (!bbr_is_probing_bandwidth(sk) && bbr->inflight_lo == ~0U) {
|
|
|
|
+ /* bbr_adapt_lower_bounds() needs cwnd before
|
|
|
|
+ * we suffered an RTO, to update inflight_lo:
|
|
|
|
+ */
|
|
|
|
+ bbr->inflight_lo =
|
|
|
|
+ max(tcp_snd_cwnd(tp), bbr->prior_cwnd);
|
|
|
|
+ }
|
|
|
|
+ } else if (bbr->prev_ca_state == TCP_CA_Loss &&
|
|
|
|
+ new_state != TCP_CA_Loss) {
|
|
|
|
+ bbr_exit_loss_recovery(sk);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
+
|
|
|
|
static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = {
|
|
|
|
- .flags = TCP_CONG_NON_RESTRICTED,
|
|
|
|
+ .flags = TCP_CONG_NON_RESTRICTED | TCP_CONG_WANTS_CE_EVENTS,
|
|
|
|
.name = "bbr",
|
|
|
|
.owner = THIS_MODULE,
|
|
|
|
.init = bbr_init,
|
|
|
|
.cong_control = bbr_main,
|
|
|
|
.sndbuf_expand = bbr_sndbuf_expand,
|
|
|
|
+ .skb_marked_lost = bbr_skb_marked_lost,
|
|
|
|
.undo_cwnd = bbr_undo_cwnd,
|
|
|
|
.cwnd_event = bbr_cwnd_event,
|
|
|
|
.ssthresh = bbr_ssthresh,
|
|
|
|
@@ -1174,10 +2356,11 @@ BTF_KFUNCS_START(tcp_bbr_check_kfunc_ids
|
|
|
|
BTF_ID_FLAGS(func, bbr_init)
|
|
|
|
BTF_ID_FLAGS(func, bbr_main)
|
|
|
|
BTF_ID_FLAGS(func, bbr_sndbuf_expand)
|
|
|
|
+BTF_ID_FLAGS(func, bbr_skb_marked_lost)
|
|
|
|
BTF_ID_FLAGS(func, bbr_undo_cwnd)
|
|
|
|
BTF_ID_FLAGS(func, bbr_cwnd_event)
|
|
|
|
BTF_ID_FLAGS(func, bbr_ssthresh)
|
|
|
|
-BTF_ID_FLAGS(func, bbr_min_tso_segs)
|
|
|
|
+BTF_ID_FLAGS(func, bbr_tso_segs)
|
|
|
|
BTF_ID_FLAGS(func, bbr_set_state)
|
|
|
|
BTF_KFUNCS_END(tcp_bbr_check_kfunc_ids)
|
|
|
|
|
|
|
|
@@ -1210,5 +2393,12 @@ MODULE_AUTHOR("Van Jacobson <vanj@google
|
|
|
|
MODULE_AUTHOR("Neal Cardwell <ncardwell@google.com>");
|
|
|
|
MODULE_AUTHOR("Yuchung Cheng <ycheng@google.com>");
|
|
|
|
MODULE_AUTHOR("Soheil Hassas Yeganeh <soheil@google.com>");
|
|
|
|
+MODULE_AUTHOR("Priyaranjan Jha <priyarjha@google.com>");
|
|
|
|
+MODULE_AUTHOR("Yousuk Seung <ysseung@google.com>");
|
|
|
|
+MODULE_AUTHOR("Kevin Yang <yyd@google.com>");
|
|
|
|
+MODULE_AUTHOR("Arjun Roy <arjunroy@google.com>");
|
|
|
|
+MODULE_AUTHOR("David Morley <morleyd@google.com>");
|
|
|
|
+
|
|
|
|
MODULE_LICENSE("Dual BSD/GPL");
|
|
|
|
MODULE_DESCRIPTION("TCP BBR (Bottleneck Bandwidth and RTT)");
|
|
|
|
+MODULE_VERSION(__stringify(BBR_VERSION));
|