Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752189AbcDTTts (ORCPT ); Wed, 20 Apr 2016 15:49:48 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:36336 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbcDTTrx (ORCPT ); Wed, 20 Apr 2016 15:47:53 -0400 From: Michal Hocko To: Andrew Morton Cc: Linus Torvalds , Johannes Weiner , Mel Gorman , David Rientjes , Tetsuo Handa , Joonsoo Kim , Hillf Danton , Vlastimil Babka , , LKML , Michal Hocko Subject: [PATCH 07/14] mm, compaction: Simplify __alloc_pages_direct_compact feedback interface Date: Wed, 20 Apr 2016 15:47:20 -0400 Message-Id: <1461181647-8039-8-git-send-email-mhocko@kernel.org> X-Mailer: git-send-email 2.8.0.rc3 In-Reply-To: <1461181647-8039-1-git-send-email-mhocko@kernel.org> References: <1461181647-8039-1-git-send-email-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5299 Lines: 158 From: Michal Hocko __alloc_pages_direct_compact communicates potential back off by two variables: - deferred_compaction tells that the compaction returned COMPACT_DEFERRED - contended_compaction is set when there is a contention on zone->lock resp. zone->lru_lock locks __alloc_pages_slowpath then backs of for THP allocation requests to prevent from long stalls. This is rather messy and it would be much cleaner to return a single compact result value and hide all the nasty details into __alloc_pages_direct_compact. This patch shouldn't introduce any functional changes. Acked-by: Vlastimil Babka Signed-off-by: Michal Hocko --- mm/page_alloc.c | 67 ++++++++++++++++++++++++++------------------------------- 1 file changed, 31 insertions(+), 36 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 06af8a757d52..350d13f3709b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2944,29 +2944,21 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, static struct page * __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, int alloc_flags, const struct alloc_context *ac, - enum migrate_mode mode, int *contended_compaction, - bool *deferred_compaction) + enum migrate_mode mode, enum compact_result *compact_result) { - enum compact_result compact_result; struct page *page; + int contended_compaction; if (!order) return NULL; current->flags |= PF_MEMALLOC; - compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac, - mode, contended_compaction); + *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac, + mode, &contended_compaction); current->flags &= ~PF_MEMALLOC; - switch (compact_result) { - case COMPACT_DEFERRED: - *deferred_compaction = true; - /* fall-through */ - case COMPACT_SKIPPED: + if (*compact_result <= COMPACT_INACTIVE) return NULL; - default: - break; - } /* * At least in one zone compaction wasn't deferred or skipped, so let's @@ -2992,6 +2984,24 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, */ count_vm_event(COMPACTFAIL); + /* + * In all zones where compaction was attempted (and not + * deferred or skipped), lock contention has been detected. + * For THP allocation we do not want to disrupt the others + * so we fallback to base pages instead. + */ + if (contended_compaction == COMPACT_CONTENDED_LOCK) + *compact_result = COMPACT_CONTENDED; + + /* + * If compaction was aborted due to need_resched(), we do not + * want to further increase allocation latency, unless it is + * khugepaged trying to collapse. + */ + if (contended_compaction == COMPACT_CONTENDED_SCHED + && !(current->flags & PF_KTHREAD)) + *compact_result = COMPACT_CONTENDED; + cond_resched(); return NULL; @@ -3000,8 +3010,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, static inline struct page * __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, int alloc_flags, const struct alloc_context *ac, - enum migrate_mode mode, int *contended_compaction, - bool *deferred_compaction) + enum migrate_mode mode, enum compact_result *compact_result) { return NULL; } @@ -3146,8 +3155,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, unsigned long pages_reclaimed = 0; unsigned long did_some_progress; enum migrate_mode migration_mode = MIGRATE_ASYNC; - bool deferred_compaction = false; - int contended_compaction = COMPACT_CONTENDED_NONE; + enum compact_result compact_result; /* * In the slowpath, we sanity check order to avoid ever trying to @@ -3245,8 +3253,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, */ page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac, migration_mode, - &contended_compaction, - &deferred_compaction); + &compact_result); if (page) goto got_pg; @@ -3259,25 +3266,14 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, * to heavily disrupt the system, so we fail the allocation * instead of entering direct reclaim. */ - if (deferred_compaction) - goto nopage; - - /* - * In all zones where compaction was attempted (and not - * deferred or skipped), lock contention has been detected. - * For THP allocation we do not want to disrupt the others - * so we fallback to base pages instead. - */ - if (contended_compaction == COMPACT_CONTENDED_LOCK) + if (compact_result == COMPACT_DEFERRED) goto nopage; /* - * If compaction was aborted due to need_resched(), we do not - * want to further increase allocation latency, unless it is - * khugepaged trying to collapse. + * Compaction is contended so rather back off than cause + * excessive stalls. */ - if (contended_compaction == COMPACT_CONTENDED_SCHED - && !(current->flags & PF_KTHREAD)) + if(compact_result == COMPACT_CONTENDED) goto nopage; } @@ -3325,8 +3321,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, */ page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac, migration_mode, - &contended_compaction, - &deferred_compaction); + &compact_result); if (page) goto got_pg; nopage: -- 2.8.0.rc3