58 lines
2.4 KiB
Diff
58 lines
2.4 KiB
Diff
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From 5f16843397798d2c709e3b8af4b1a73539d13aa8 Mon Sep 17 00:00:00 2001
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From: Sultan Alsawaf <sultan@kerneltoast.com>
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Date: Sat, 28 Mar 2020 13:06:28 -0700
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Subject: ZEN: INTERACTIVE: mm: Disable watermark boosting by default
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What watermark boosting does is preemptively fire up kswapd to free
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memory when there hasn't been an allocation failure. It does this by
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increasing kswapd's high watermark goal and then firing up kswapd. The
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reason why this causes freezes is because, with the increased high
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watermark goal, kswapd will steal memory from processes that need it in
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order to make forward progress. These processes will, in turn, try to
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allocate memory again, which will cause kswapd to steal necessary pages
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from those processes again, in a positive feedback loop known as page
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thrashing. When page thrashing occurs, your system is essentially
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livelocked until the necessary forward progress can be made to stop
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processes from trying to continuously allocate memory and trigger
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kswapd to steal it back.
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This problem already occurs with kswapd *without* watermark boosting,
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but it's usually only encountered on machines with a small amount of
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memory and/or a slow CPU. Watermark boosting just makes the existing
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problem worse enough to notice on higher spec'd machines.
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Disable watermark boosting by default since it's a total dumpster fire.
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I can't imagine why anyone would want to explicitly enable it, but the
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option is there in case someone does.
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Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
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---
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init/Kconfig | 1 +
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mm/page_alloc.c | 4 ++++
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2 files changed, 5 insertions(+)
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--- a/init/Kconfig
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+++ b/init/Kconfig
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@@ -151,6 +151,7 @@ config ZEN_INTERACTIVE
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MG-LRU minimum cache TTL.......: 0 -> 1000 ms
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Compact unevictable............: yes -> no
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Compaction proactiveness.......: 20 -> 0
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+ Watermark boost factor.........: 1.5 -> 0
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--- EEVDF CPU Scheduler --------------------------------
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--- a/mm/page_alloc.c
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+++ b/mm/page_alloc.c
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@@ -271,7 +271,11 @@ const char * const migratetype_names[MIG
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int min_free_kbytes = 1024;
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int user_min_free_kbytes = -1;
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+#ifdef CONFIG_ZEN_INTERACTIVE
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+static int watermark_boost_factor __read_mostly;
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+#else
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static int watermark_boost_factor __read_mostly = 15000;
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+#endif
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static int watermark_scale_factor = 10;
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/* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
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