linux-kernel - [PATCH] Documentation/sysctl: document page_lock

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Date:   Fri, 25 Mar 2022 12:44:37 -0400
From:   Joel Savitz <jsavitz@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Joel Savitz <jsavitz@...hat.com>, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Mike Rapoport <rppt@...nel.org>,
        "zhangyi (F)" <yi.zhang@...wei.com>,
        Charan Teja Reddy <charante@...eaurora.org>,
        linux-doc@...r.kernel.org
Subject: [PATCH] Documentation/sysctl: document page_lock_unfairness

commit 5ef64cc8987a ("mm: allow a controlled amount of unfairness in the page lock")
introduced a new systctl but no accompanying documentation.

Add a simple entry to the documentation.

Signed-off-by: Joel Savitz <jsavitz@...hat.com>
---
 Documentation/admin-guide/sysctl/vm.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
index f4804ce37c58..747e325ebcd0 100644
--- a/Documentation/admin-guide/sysctl/vm.rst
+++ b/Documentation/admin-guide/sysctl/vm.rst
@@ -62,6 +62,7 @@ Currently, these files are in /proc/sys/vm:
 - overcommit_memory
 - overcommit_ratio
 - page-cluster
+- page_lock_unfairness
 - panic_on_oom
 - percpu_pagelist_high_fraction
 - stat_interval
@@ -754,6 +755,14 @@ extra faults and I/O delays for following faults if they would have been part of
 that consecutive pages readahead would have brought in.
 
 
+page_lock_unfairness
+====================
+
+This value determines the number of times that the page lock can be
+stolen from under a waiter. After the lock is stolen the number of times
+specified in this file (default is 5), the "fair lock handoff" semantics
+will apply, and the waiter will only be awakened if the lock can be taken.
+
 panic_on_oom
 ============
 
-- 
2.27.0