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authorDavid Rientjes <rientjes@google.com>2009-06-16 15:32:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:43 -0700
commit4d8b9135c30ccbe46e621fefd862969819003fd6 (patch)
tree47674640c8a65b3ba440b2dc224efbab7571c638 /mm
parent2ff05b2b4eac2e63d345fc731ea151a060247f53 (diff)
downloadlinux-4d8b9135c30ccbe46e621fefd862969819003fd6.tar.gz
oom: avoid unnecessary mm locking and scanning for OOM_DISABLE
This moves the check for OOM_DISABLE to the badness heuristic so it is only necessary to hold task_lock() once. If the mm is OOM_DISABLE, the score is 0, which is also correctly exported via /proc/pid/oom_score. This requires that tasks with badness scores of 0 are prohibited from being oom killed, which makes sense since they would not allow for future memory freeing anyway. Since the oom_adj value is a characteristic of an mm and not a task, it is no longer necessary to check the oom_adj value for threads sharing the same memory (except when simply issuing SIGKILLs for threads in other thread groups). Cc: Nick Piggin <npiggin@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/oom_kill.c42
1 files changed, 10 insertions, 32 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index b60913520ef..cdcf89cb9ff 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -67,6 +67,10 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
return 0;
}
oom_adj = mm->oom_adj;
+ if (oom_adj == OOM_DISABLE) {
+ task_unlock(p);
+ return 0;
+ }
/*
* The memory size of the process is the basis for the badness.
@@ -253,15 +257,8 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
*ppoints = ULONG_MAX;
}
- task_lock(p);
- if (p->mm && p->mm->oom_adj == OOM_DISABLE) {
- task_unlock(p);
- continue;
- }
- task_unlock(p);
-
points = badness(p, uptime.tv_sec);
- if (points > *ppoints || !chosen) {
+ if (points > *ppoints) {
chosen = p;
*ppoints = points;
}
@@ -354,32 +351,13 @@ static int oom_kill_task(struct task_struct *p)
struct mm_struct *mm;
struct task_struct *g, *q;
+ task_lock(p);
mm = p->mm;
-
- /* WARNING: mm may not be dereferenced since we did not obtain its
- * value from get_task_mm(p). This is OK since all we need to do is
- * compare mm to q->mm below.
- *
- * Furthermore, even if mm contains a non-NULL value, p->mm may
- * change to NULL at any time since we do not hold task_lock(p).
- * However, this is of no concern to us.
- */
-
- if (mm == NULL)
+ if (!mm || mm->oom_adj == OOM_DISABLE) {
+ task_unlock(p);
return 1;
-
- /*
- * Don't kill the process if any threads are set to OOM_DISABLE
- */
- do_each_thread(g, q) {
- task_lock(q);
- if (q->mm == mm && q->mm && q->mm->oom_adj == OOM_DISABLE) {
- task_unlock(q);
- return 1;
- }
- task_unlock(q);
- } while_each_thread(g, q);
-
+ }
+ task_unlock(p);
__oom_kill_task(p, 1);
/*