[079/146] mm/pagealloc: sysctl: change watermark_scale_factor max limit to 30%

Commit Message

Andrew Morton Jan. 14, 2022, 10:07 p.m. UTC

From: Suren Baghdasaryan <[e-mail]>
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/[e-mail]
Signed-off-by: Suren Baghdasaryan <[e-mail]>
Acked-by: Johannes Weiner <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Lukas Middendorf <[e-mail]>
Cc: Antti Palosaari <[e-mail]>
Cc: Luis Chamberlain <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Iurii Zaikin <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Zhang Yi <[e-mail]>
Cc: Fengfei Xi <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 Documentation/admin-guide/sysctl/vm.rst |    2 +-
 kernel/sysctl.c                         |    3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

Patch

--- 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",