Re: [patch 00/10 -mm v3] oom killer rewrite

[David Rientjes <rientjes@google.com>]

On Fri, 12 Mar 2010, KAMEZAWA Hiroyuki wrote:

> BTW, it seems there are still chances for serial-oom-killer.
> 
> Assume I run memory eater (called malloc) on a host.
> ==
> Mar 13 13:05:56 localhost kernel: malloc invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0, oom_score_adj=0
> Mar 13 13:05:56 localhost kernel: malloc cpuset=/ mems_allowed=0
> Mar 13 13:05:56 localhost kernel: Pid: 2525, comm: malloc Not tainted 2.6.34-rc1-mm1+ #3
> Mar 13 13:05:56 localhost kernel: Call Trace:
> Mar 13 13:05:56 localhost kernel: [<ffffffff8108aebf>] ? cpuset_print_task_mems_allowed+0x91/0x9c
> Mar 13 13:05:56 localhost kernel: [<ffffffff810c90c1>] dump_header+0x74/0x1af
> <snip>
> Mar 13 13:05:56 localhost kernel: [ 2525]   500  2525   434340   433346   0       0             0 malloc
> Mar 13 13:05:56 localhost kernel: Out of memory: Kill process 2525 (malloc) with score 967 or sacrifice child
> Mar 13 13:05:56 localhost kernel: Killed process 2525 (malloc) total-vm:1737360kB, anon-rss:1733364kB, file-rss:20kB
> Mar 13 13:05:56 localhost kernel: rsyslogd invoked oom-killer: gfp_mask=0x201da, order=0, oom_adj=0, oom_score_adj=0
> Mar 13 13:05:56 localhost kernel: rsyslogd cpuset=/ mems_allowed=0
> Mar 13 13:05:56 localhost kernel: Pid: 696, comm: rsyslogd Not tainted 2.6.34-rc1-mm1+ #3
> Mar 13 13:05:56 localhost kernel: Call Trace:
> Mar 13 13:05:56 localhost kernel: [<ffffffff8108aebf>] ? cpuset_print_task_mems_allowed+0x91/0x9c
> Mar 13 13:05:56 localhost kernel: [<ffffffff810c90c1>] dump_header+0x74/0x1af
> Mar 13 13:05:56 localhost kernel: [<ffffffff81211a8e>] ? ___ratelimit+0xe6/0x104
> Mar 13 13:05:56 localhost kernel: [<ffffffff810c942a>] oom_kill_process+0x49/0x1ed
> <snip>
> Mar 13 13:05:56 localhost kernel: 480 total pagecache pages
> Mar 13 13:05:56 localhost kernel: 0 pages in swap cache
> Mar 13 13:05:56 localhost kernel: Swap cache stats: add 0, delete 0, find 0/0
> Mar 13 13:05:56 localhost kernel: Free swap  = 0kB
> Mar 13 13:05:56 localhost kernel: Total swap = 0kB
> Mar 13 13:05:56 localhost kernel: 2097151 pages RAM
> Mar 13 13:05:56 localhost kernel: 48776 pages reserved
> Mar 13 13:05:56 localhost kernel: 1356 pages shared
> Mar 13 13:05:56 localhost kernel: 458132 pages non-shared
> <snip>
> Mar 13 13:05:56 localhost kernel: [ 2506]     0  2506     3120       55   0       0             0 anacron
> Mar 13 13:05:56 localhost kernel: Out of memory: Kill process 1267 (gdm-simple-gree) with score 2 or sacrifice child
> Mar 13 13:05:56 localhost kernel: Killed process 1267 (gdm-simple-gree) total-vm:359156kB, anon-rss:4012kB, file-rss:472kB
> ==
> 
> Then, at first, malloc, a bad program is killed. But, another oom-kill happens immediately and 
> gdm-simple-gree is killed.
> 
> I think there is a task as !p->mm but TIF_MEMDIE task in tasklist.
> 

Perhaps, but we should probably handle exit racing conditions with 
PF_EXITING instead of TIF_MEMDIE.  We also need to filter these tasks 
according to memcg and cpusets since oom killed tasks in other cgroups 
shouldn't make the oom killer a no-op for current.

I'll add this:
---
 mm/oom_kill.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -290,12 +290,6 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
 	for_each_process(p) {
 		unsigned int points;
 
-		/*
-		 * skip kernel threads and tasks which have already released
-		 * their mm.
-		 */
-		if (!p->mm)
-			continue;
 		/* skip the init task */
 		if (is_global_init(p))
 			continue;
@@ -336,6 +330,12 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
 			*ppoints = 1000;
 		}
 
+		/*
+		 * skip kernel threads and tasks which have already released
+		 * their mm.
+		 */
+		if (!p->mm)
+			continue;
 		if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 			continue;
 

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