From: Suren Baghdasaryan surenb@google.com

mainline inclusion from mainline-v5.17-rc1 commit 39c65a94cd9661532be150e88f8b02f4a6844a35 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I7T82I CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

Upstream commit 39c65a94cd96 change watermark_scale_factor max limit to 30%, but we don't backport it.

The current limit of watermark_scale_factor is 10%. As described in the patch, the limit of watermark_scale_factor may need to be increased in some scenarios to reduce application performance fluctuations due to direct recycling.

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For embedded systems with low total memory, having to run applications with relatively large memory requirements, 10% max limitation for watermark_scale_factor poses an issue of triggering direct reclaim every time such application is started. This results in slow application startup times and bad end-user experience.

By increasing watermark_scale_factor max limit we allow vendors more flexibility to choose the right level of kswapd aggressiveness for their device and workload requirements.

Link: https://lkml.kernel.org/r/20211124193604.2758863-1-surenb@google.com Signed-off-by: Suren Baghdasaryan surenb@google.com Acked-by: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@suse.com Cc: Lukas Middendorf kernel@tuxforce.de Cc: Antti Palosaari crope@iki.fi Cc: Luis Chamberlain mcgrof@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Iurii Zaikin yzaikin@google.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Mel Gorman mgorman@techsingularity.net Cc: Jonathan Corbet corbet@lwn.net Cc: Zhang Yi yi.zhang@huawei.com Cc: Fengfei Xi xi.fengfei@h3c.com Cc: Mike Rapoport rppt@kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- Documentation/admin-guide/sysctl/vm.rst | 2 +- kernel/sysctl.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index a84bef7aa864..06500c423592 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -996,7 +996,7 @@ how much memory needs to be free before kswapd goes back to sleep.

The unit is in fractions of 10,000. The default value of 10 means the distances between watermarks are 0.1% of the available memory in the -node/system. The maximum value is 1000, or 10% of memory. +node/system. The maximum value is 3000, or 30% of memory.

A high rate of threads entering direct reclaim (allocstall) or kswapd going to sleep prematurely (kswapd_low_wmark_hit_quickly) can indicate diff --git a/kernel/sysctl.c b/kernel/sysctl.c index d290ba2d8fee..fd82beb9a743 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -122,6 +122,7 @@ static unsigned long long_max = LONG_MAX; static int one_hundred = 100; static int two_hundred = 200; static int one_thousand = 1000; +static int three_thousand = 3000; #ifdef CONFIG_PRINTK static int ten_thousand = 10000; #endif @@ -2983,7 +2984,7 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = watermark_scale_factor_sysctl_handler, .extra1 = SYSCTL_ONE, - .extra2 = &one_thousand, + .extra2 = &three_thousand, }, { .procname = "percpu_pagelist_fraction",