mm: replace hardcoded 3% with admin_reserve_pages knob
Add an admin_reserve_kbytes knob to allow admins to change the hardcoded
memory reserve to something other than 3%, which may be multiple
gigabytes on large memory systems. Only about 8MB is necessary to
enable recovery in the default mode, and only a few hundred MB are
required even when overcommit is disabled.
This affects OVERCOMMIT_GUESS and OVERCOMMIT_NEVER.
admin_reserve_kbytes is initialized to min(3% free pages, 8MB)
I arrived at 8MB by summing the RSS of sshd or login, bash, and top.
Please see first patch in this series for full background, motivation,
testing, and full changelog.
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: make init_admin_reserve() static]
Signed-off-by: Andrew Shewmaker <agshew@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6daabb7..9edcf45 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1436,6 +1436,13 @@
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
+ {
+ .procname = "admin_reserve_kbytes",
+ .data = &sysctl_admin_reserve_kbytes,
+ .maxlen = sizeof(sysctl_admin_reserve_kbytes),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ },
{ }
};
