On 15.08.2016 20:12, Joonsoo Kim wrote:
> On Mon, Aug 15, 2016 at 11:16:36AM +0200, Vlastimil Babka wrote:
>> On 08/15/2016 06:48 AM, Ralf-Peter Rohbeck wrote:
>>> On 02.08.2016 12:25, Ralf-Peter Rohbeck wrote:
>>> Took me a little longer than expected due to work. The failure wouldn't
>>> happen for a while and so I started a couple of scripts and let them
>>> run. When I checked today the server didn't respond on the network and
>>> sure enough it had killed everything. This is with 4.7.0 with the config
>>> based on Debian 4.7-rc7.
>>>
>>> trace_pipe got a little big (5GB) so I uploaded the logs to
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__filebin.net_box0wycfouvhl6sr_OOM-5F4.7.0.tar.bz2&d=DQIBAg&c=8S5idjlO_n28Ko3lg6lskTMwneSC-WqZ5EBTEEvDlkg&r=yGQdEpZknbtYvR0TyhkCGu-ifLklIvXIf740poRFltQ&m=5VwXI8Iw4BejxSrNmLdOj-bp6ZZXeBJ_-ENR4F0NToo&s=KuzRUwyq4itin6x-UJT-XYbJ9q0tOSt3zQuEYZyHKqE&e= . before_btrfs is
>>> before the btrfs filesystems were mounted.
>>> I did run a btrfs balance because it creates IO load and I needed to
>>> balance anyway. Maybe that's what caused it?
>> pgmigrate_success        46738962
>> pgmigrate_fail          135649772
>> compact_migrate_scanned 309726659
>> compact_free_scanned   9715615169
>> compact_isolated        229689596
>> compact_stall 4777
>> compact_fail 3068
>> compact_success 1709
>> compact_daemon_wake 207834
>>
>> The migration failures are quite enormous. Very quick analysis of the
>> trace seems to confirm that these are mostly "real", as opposed to result
>> of failure to isolate free pages for migration targets, although the free
>> scanner spent a lot of time:
> I don't think that main reason of OOM is 'real' migration failure.
> If it is the case, compaction would find next migratable pages and
> eventually some of pages would be migrated successfully.
>
> pagetypeinfo shows that there are too many unmovable pageblock.
> Freepage scanner don't scan those pageblocks so there is a large
> possibility that it cannot find freepages even if the system has many
> freepages. I think that this is the root cause of the problem.
>
> It's better to check that following work-around help the problem.
>
> Thanks.
>
> ------------>8-----------
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 9affb29..965eddd 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1082,10 +1082,6 @@ static void isolate_freepages(struct compact_control *cc)
>                  if (!page)
>                          continue;
>   
> -               /* Check the block is suitable for migration */
> -               if (!suitable_migration_target(page))
> -                       continue;
> -
>                  /* If isolation recently failed, do not retry */
>                  if (!isolation_suitable(cc, page))
>                          continue;
>
That seemed to help a little (subjectively) but still OOM killed a 
kernel build. The logs are attached.

Thanks,
Ralf-Peter


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