linux/debian/patches/patchset-zen/sauce/0015-ZEN-INTERACTIVE-Tune-EEVDF-for-interactivity.patch

From 9e5b04df7190ab4750ae3c67714fd537ef4d79f5 Mon Sep 17 00:00:00 2001
From: "Jan Alexander Steffens (heftig)" <heftig@archlinux.org>
Date: Tue, 31 Oct 2023 19:03:10 +0100
Subject: ZEN: INTERACTIVE: Tune EEVDF for interactivity

5.7:
Take "sysctl_sched_nr_migrate" tune from early XanMod builds of 128. As
of 5.7, XanMod uses 256 but that may affect applications that require
timely response to IRQs.

5.15:
Per [a comment][1] on our ZEN INTERACTIVE commit, reducing the cost of
migration causes the system less responsive under high load.  Most
likely the combination of reduced migration cost + the higher number of
tasks that can be migrated at once contributes to this.

To better handle this situation, restore the mainline migration cost
value and also reduce the max number of tasks that can be migrated in
batch from 128 to 64.

If this doesn't help, we'll restore the reduced migration cost and keep
total number of tasks that can be migrated at once to 32.

[1]: https://github.com/zen-kernel/zen-kernel/commit/be5ba234ca0a5aabe74bfc7e1f636f085bd3823c#commitcomment-63159674

6.6:
Port the tuning to EEVDF, which removed a couple of settings.

6.7:
Instead of increasing the number of tasks that migrate at once, migrate
the amount acceptable for PREEMPT_RT, but reduce the cost so migrations
occur more often.

This should make CFS/EEVDF behave more like out-of-tree schedulers that
aggressively use idle cores to reduce latency, but without the jank
caused by rebalancing too many tasks at once.
---
 init/Kconfig         |  7 +++++++
 kernel/sched/fair.c  | 13 +++++++++++++
 kernel/sched/sched.h |  2 +-
 3 files changed, 21 insertions(+), 1 deletion(-)

--- a/init/Kconfig
+++ b/init/Kconfig
@@ -169,6 +169,13 @@ config ZEN_INTERACTIVE
 
 	    Background-reclaim hugepages...:   no   ->   yes
 
+	  --- EEVDF CPU Scheduler --------------------------------
+
+	    Minimal granularity............:   0.75 ->   0.4  ms
+	    Migration cost.................:   0.5  ->   0.25 ms
+	    Bandwidth slice size...........:   5    ->   3    ms
+	    Task rebalancing threshold.....:  32    ->   8
+
 config BROKEN
 	bool
 
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -73,10 +73,19 @@ unsigned int sysctl_sched_tunable_scalin
  *
  * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
+#ifdef CONFIG_ZEN_INTERACTIVE
+unsigned int sysctl_sched_base_slice			= 400000ULL;
+static unsigned int normalized_sysctl_sched_base_slice	= 400000ULL;
+#else
 unsigned int sysctl_sched_base_slice			= 750000ULL;
 static unsigned int normalized_sysctl_sched_base_slice	= 750000ULL;
+#endif
 
+#ifdef CONFIG_ZEN_INTERACTIVE
+const_debug unsigned int sysctl_sched_migration_cost	= 250000UL;
+#else
 const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
+#endif
 
 static int __init setup_sched_thermal_decay_shift(char *str)
 {
@@ -121,8 +130,12 @@ int __weak arch_asym_cpu_priority(int cp
  *
  * (default: 5 msec, units: microseconds)
  */
+#ifdef CONFIG_ZEN_INTERACTIVE
+static unsigned int sysctl_sched_cfs_bandwidth_slice		= 3000UL;
+#else
 static unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
 #endif
+#endif
 
 #ifdef CONFIG_NUMA_BALANCING
 /* Restrict the NUMA promotion throughput (MB/s) for each target node. */
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2816,7 +2816,7 @@ extern void deactivate_task(struct rq *r
 
 extern void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags);
 
-#ifdef CONFIG_PREEMPT_RT
+#if defined(CONFIG_PREEMPT_RT) || defined(CONFIG_ZEN_INTERACTIVE)
 # define SCHED_NR_MIGRATE_BREAK 8
 #else
 # define SCHED_NR_MIGRATE_BREAK 32