From: Suren Baghdasaryan <surenb@xxxxxxxxxx> Subject: mm/pagealloc: sysctl: change watermark_scale_factor max limit to 30% 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@xxxxxxxxxx Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Lukas Middendorf <kernel@xxxxxxxxxxx> Cc: Antti Palosaari <crope@xxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Iurii Zaikin <yzaikin@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Zhang Yi <yi.zhang@xxxxxxxxxx> Cc: Fengfei Xi <xi.fengfei@xxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/sysctl/vm.rst | 2 +- kernel/sysctl.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-) --- a/Documentation/admin-guide/sysctl/vm.rst~sysctl-change-watermark_scale_factor-max-limit-to-30% +++ a/Documentation/admin-guide/sysctl/vm.rst @@ -948,7 +948,7 @@ how much memory needs to be free before 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 --- a/kernel/sysctl.c~sysctl-change-watermark_scale_factor-max-limit-to-30% +++ a/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 @@ -2959,7 +2960,7 @@ 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_high_fraction", _
