[PATCH] Documentation/sysctl: document page_lock_unfairness

[PATCH] Documentation/sysctl: document page_lock_unfairness

[Joel Savitz]

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@redhat.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