linux-kernel - [PATCH] mm/page_alloc: Introduce vm.percpu_pagelist_high

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Date:   Fri, 28 May 2021 16:10:10 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, Hillf Danton <hdanton@...a.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Michal Hocko <mhocko@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: [PATCH] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction
 -fix

Vlastimil Babka pointed out that the documentation for
vm.percpu_pagelist_high_fraction is potentially misleading so fix it.

This is a fix to the mmotm patch
mm-page_alloc-introduce-vmpercpu_pagelist_high_fraction.patch

Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
---
 Documentation/admin-guide/sysctl/vm.rst | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index e85c2f21d209..2da25735a629 100644
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -793,15 +793,16 @@ why oom happens. You can get snapshot.
 percpu_pagelist_high_fraction
 =============================
 
-This is the fraction of pages in each zone that are allocated for each
-per cpu page list.  The min value for this is 8.  It means that we do
-not allow more than 1/8th of pages in each zone to be allocated in any
-single per_cpu_pagelist.  This entry only changes the value of hot per
-cpu pagelists. User can specify a number like 100 to allocate 1/100th
-of each zone to each per cpu page list.
-
-The batch value of each per cpu pagelist remains the same regardless of the
-value of the high fraction so allocation latencies are unaffected.
+This is the fraction of pages in each zone that are can be stored to
+per-cpu page lists. It is an upper boundary that is divided depending
+on the number of online CPUs. The min value for this is 8 which means
+that we do not allow more than 1/8th of pages in each zone to be stored
+on per-cpu page lists. This entry only changes the value of hot per-cpu
+page lists. A user can specify a number like 100 to allocate 1/100th of
+each zone between per-cpu lists.
+
+The batch value of each per-cpu page list remains the same regardless of
+the value of the high fraction so allocation latencies are unaffected.
 
 The initial value is zero. Kernel uses this value to set the high pcp->high
 mark based on the low watermark for the zone and the number of local