[patch] mm, oom: base root bonus on current usage

David Rientjes
2014-01-26T03:48:39Z

A 3% of system memory bonus is sometimes too excessive in comparison to
other processes and can yield poor results when all processes on the
system are root and none of them use over 3% of memory.

Replace the 3% of system memory bonus with a 3% of current memory usage
bonus.

Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: David Rientjes <rientjes@google.com>
---
Documentation/filesystems/proc.txt | 4 ++--
mm/oom_kill.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1386,8 +1386,8 @@ may allocate from based on an estimation of its current memory and swap use.
For example, if a task is using all allowed memory, its badness score will be
1000. If it is using half of its allowed memory, its score will be 500.

-There is an additional factor included in the badness score: root
-processes are given 3% extra memory over other tasks.
+There is an additional factor included in the badness score: the current memory
+and swap usage is discounted by 3% for root processes.

The amount of "allowed" memory depends on the context in which the oom killer
was called. If it is due to the memory assigned to the allocating task's cpuset
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -178,7 +178,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
* implementation used by LSMs.
*/
if (has_capability_noaudit(p, CAP_SYS_ADMIN))
- adj -= 30;
+ points -= (points * 3) / 100;

/* Normalize to oom_score_adj units */
adj *= totalpages / 1000;