From: Michal Hocko <mhocko@xxxxxxxx> Subject: mm, oom: protect !costly allocations some more for !CONFIG_COMPACTION Joonsoo has reported that he is able to trigger OOM for !costly high order requests (heavy fork() workload close the OOM) with the new oom detection rework. This is because we rely only on should_reclaim_retry when the compaction is disabled and it only checks watermarks for the requested order and so we might trigger OOM when there is a lot of free memory. It is not very clear what are the usual workloads when the compaction is disabled. Relying on high order allocations heavily without any mechanism to create those orders except for unbound amount of reclaim is certainly not a good idea. To prevent from potential regressions let's help this configuration some. We have to sacrifice the determinsm though because there simply is none here possible. should_compact_retry implementation for !CONFIG_COMPACTION, which was empty so far, will do watermark check for order-0 on all eligible zones. This will cause retrying until either the reclaim cannot make any further progress or all the zones are depleted even for order-0 pages. This means that the number of retries is basically unbounded for !costly orders but that was the case before the rework as well so this shouldn't regress. [akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes] Link: http://lkml.kernel.org/r/1463051677-29418-3-git-send-email-mhocko@xxxxxxxxxx Reported-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff -puN mm/page_alloc.c~mm-oom-protect-costly-allocations-some-more-for-config_compaction mm/page_alloc.c --- a/mm/page_alloc.c~mm-oom-protect-costly-allocations-some-more-for-config_compaction +++ a/mm/page_alloc.c @@ -3317,6 +3317,24 @@ should_compact_retry(struct alloc_contex enum migrate_mode *migrate_mode, int compaction_retries) { + struct zone *zone; + struct zoneref *z; + + if (!order || order > PAGE_ALLOC_COSTLY_ORDER) + return false; + + /* + * There are setups with compaction disabled which would prefer to loop + * inside the allocator rather than hit the oom killer prematurely. + * Let's give them a good hope and keep retrying while the order-0 + * watermarks are OK. + */ + for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, + ac->nodemask) { + if (zone_watermark_ok(zone, 0, min_wmark_pages(zone), + ac_classzone_idx(ac), alloc_flags)) + return true; + } return false; } #endif /* CONFIG_COMPACTION */ _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
