Hi, there have been multiple reports [1][2][3][4][5] about pre-mature OOM killer invocations since 4.7 which contains oom detection rework. All of them were for order-2 (kernel stack) alloaction requests failing because of a high fragmentation and compaction failing to make any forward progress. While investigating this we have found out that the compaction just gives up too early. Vlastimil has been working on compaction improvement for quite some time and his series [6] is already sitting in mmotm tree. This already helps a lot because it drops some heuristics which are more aimed at lower latencies for high orders rather than reliability. Joonsoo has then identified further problem with too many blocks being marked as unmovable [7] and Vlastimil has prepared a patch on top of his series [8] which is also in the mmotm tree now. That being said, the regression is real and should be fixed for 4.7 stable users. [6][8] was reported to help and ooms are no longer reproducible. I know we are quite late (rc3) in 4.8 but I would vote for mergeing those patches and have them in 4.8. For 4.7 I would go with a partial revert of the detection rework for high order requests (see patch below). This patch is really trivial. If those compaction improvements are just too large for 4.8 then we can use the same patch as for 4.7 stable for now and revert it in 4.9 after compaction changes are merged. Thoughts? [1] http://lkml.kernel.org/r/20160731051121.GB307@x4 [2] http://lkml.kernel.org/r/201608120901.41463.a.miskiewicz@xxxxxxxxx [3] http://lkml.kernel.org/r/20160801192620.GD31957@xxxxxxxxxxxxxx [4] https://lists.opensuse.org/opensuse-kernel/2016-08/msg00021.html [5] https://bugzilla.opensuse.org/show_bug.cgi?id=994066 [6] http://lkml.kernel.org/r/20160810091226.6709-1-vbabka@xxxxxxx [7] http://lkml.kernel.org/r/20160816031222.GC16913@js1304-P5Q-DELUXE [8] http://lkml.kernel.org/r/f7a9ea9d-bb88-bfd6-e340-3a933559305a@xxxxxxx --- >From 899b738538de41295839dca2090a774bdd17acd2 Mon Sep 17 00:00:00 2001 From: Michal Hocko <mhocko@xxxxxxxx> Date: Mon, 22 Aug 2016 10:52:06 +0200 Subject: [PATCH] mm, oom: prevent pre-mature OOM killer invocation for high order request There have been several reports about pre-mature OOM killer invocation in 4.7 kernel when order-2 allocation request (for the kernel stack) invoked OOM killer even during basic workloads (light IO or even kernel compile on some filesystems). In all reported cases the memory is fragmented and there are no order-2+ pages available. There is usually a large amount of slab memory (usually dentries/inodes) and further debugging has shown that there are way too many unmovable blocks which are skipped during the compaction. Multiple reporters have confirmed that the current linux-next which includes [1] and [2] helped and OOMs are not reproducible anymore. A simpler fix for the stable is to simply ignore the compaction feedback and retry as long as there is a reclaim progress for high order requests which we used to do before. We already do that for CONFING_COMPACTION=n so let's reuse the same code when compaction is enabled as well. [1] http://lkml.kernel.org/r/20160810091226.6709-1-vbabka@xxxxxxx [2] http://lkml.kernel.org/r/f7a9ea9d-bb88-bfd6-e340-3a933559305a@xxxxxxx Fixes: 0a0337e0d1d1 ("mm, oom: rework oom detection") Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> --- mm/page_alloc.c | 50 ++------------------------------------------------ 1 file changed, 2 insertions(+), 48 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8b3e1341b754..6e354199151b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3254,53 +3254,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, return NULL; } -static inline bool -should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, - enum compact_result compact_result, enum migrate_mode *migrate_mode, - int compaction_retries) -{ - int max_retries = MAX_COMPACT_RETRIES; - - if (!order) - return false; - - /* - * compaction considers all the zone as desperately out of memory - * so it doesn't really make much sense to retry except when the - * failure could be caused by weak migration mode. - */ - if (compaction_failed(compact_result)) { - if (*migrate_mode == MIGRATE_ASYNC) { - *migrate_mode = MIGRATE_SYNC_LIGHT; - return true; - } - return false; - } - - /* - * make sure the compaction wasn't deferred or didn't bail out early - * due to locks contention before we declare that we should give up. - * But do not retry if the given zonelist is not suitable for - * compaction. - */ - if (compaction_withdrawn(compact_result)) - return compaction_zonelist_suitable(ac, order, alloc_flags); - - /* - * !costly requests are much more important than __GFP_REPEAT - * costly ones because they are de facto nofail and invoke OOM - * killer to move on while costly can fail and users are ready - * to cope with that. 1/4 retries is rather arbitrary but we - * would need much more detailed feedback from compaction to - * make a better decision. - */ - if (order > PAGE_ALLOC_COSTLY_ORDER) - max_retries /= 4; - if (compaction_retries <= max_retries) - return true; - - return false; -} #else static inline struct page * __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, @@ -3311,6 +3264,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, return NULL; } +#endif /* CONFIG_COMPACTION */ + static inline bool should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags, enum compact_result compact_result, @@ -3337,7 +3292,6 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla } return false; } -#endif /* CONFIG_COMPACTION */ /* Perform direct synchronous page reclaim */ static int -- 2.8.1 -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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