Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752046AbcDTTr6 (ORCPT ); Wed, 20 Apr 2016 15:47:58 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:33556 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751889AbcDTTrz (ORCPT ); Wed, 20 Apr 2016 15:47:55 -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 08/14] mm, compaction: Abstract compaction feedback to helpers Date: Wed, 20 Apr 2016 15:47:21 -0400 Message-Id: <1461181647-8039-9-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: 3851 Lines: 124 From: Michal Hocko Compaction can provide a wild variation of feedback to the caller. Many of them are implementation specific and the caller of the compaction (especially the page allocator) shouldn't be bound to specifics of the current implementation. This patch abstracts the feedback into three basic types: - compaction_made_progress - compaction was active and made some progress. - compaction_failed - compaction failed and further attempts to invoke it would most probably fail and therefore it is not worth retrying - compaction_withdrawn - compaction wasn't invoked for an implementation specific reasons. In the current implementation it means that the compaction was deferred, contended or the page scanners met too early without any progress. Retrying is still worthwhile. [vbabka@suse.cz: do not change thp back off behavior] Signed-off-by: Michal Hocko --- include/linux/compaction.h | 79 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) diff --git a/include/linux/compaction.h b/include/linux/compaction.h index a7b9091ff349..a002ca55c513 100644 --- a/include/linux/compaction.h +++ b/include/linux/compaction.h @@ -78,6 +78,70 @@ extern void compaction_defer_reset(struct zone *zone, int order, bool alloc_success); extern bool compaction_restarting(struct zone *zone, int order); +/* Compaction has made some progress and retrying makes sense */ +static inline bool compaction_made_progress(enum compact_result result) +{ + /* + * Even though this might sound confusing this in fact tells us + * that the compaction successfully isolated and migrated some + * pageblocks. + */ + if (result == COMPACT_PARTIAL) + return true; + + return false; +} + +/* Compaction has failed and it doesn't make much sense to keep retrying. */ +static inline bool compaction_failed(enum compact_result result) +{ + /* All zones where scanned completely and still not result. */ + if (result == COMPACT_COMPLETE) + return true; + + return false; +} + +/* + * Compaction has backed off for some reason. It might be throttling or + * lock contention. Retrying is still worthwhile. + */ +static inline bool compaction_withdrawn(enum compact_result result) +{ + /* + * Compaction backed off due to watermark checks for order-0 + * so the regular reclaim has to try harder and reclaim something. + */ + if (result == COMPACT_SKIPPED) + return true; + + /* + * If compaction is deferred for high-order allocations, it is + * because sync compaction recently failed. If this is the case + * and the caller requested a THP allocation, we do not want + * to heavily disrupt the system, so we fail the allocation + * instead of entering direct reclaim. + */ + if (result == COMPACT_DEFERRED) + return true; + + /* + * If compaction in async mode encounters contention or blocks higher + * priority task we back off early rather than cause stalls. + */ + if (result == COMPACT_CONTENDED) + return true; + + /* + * Page scanners have met but we haven't scanned full zones so this + * is a back off in fact. + */ + if (result == COMPACT_PARTIAL_SKIPPED) + return true; + + return false; +} + extern int kcompactd_run(int nid); extern void kcompactd_stop(int nid); extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx); @@ -114,6 +178,21 @@ static inline bool compaction_deferred(struct zone *zone, int order) return true; } +static inline bool compaction_made_progress(enum compact_result result) +{ + return false; +} + +static inline bool compaction_failed(enum compact_result result) +{ + return false; +} + +static inline bool compaction_withdrawn(enum compact_result result) +{ + return true; +} + static inline int kcompactd_run(int nid) { return 0; -- 2.8.0.rc3