From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756282AbcIFNxX (ORCPT ); Tue, 6 Sep 2016 09:53:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:49581 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753565AbcIFNxR (ORCPT ); Tue, 6 Sep 2016 09:53:17 -0400 From: Vlastimil Babka To: Michal Hocko , Andrew Morton , Arkadiusz Miskiewicz , Ralf-Peter Rohbeck , Olaf Hering Cc: linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Vlastimil Babka , Mel Gorman , Joonsoo Kim , David Rientjes , Rik van Riel , Michal Hocko Subject: [PATCH 2/4] mm, compaction: more reliably increase direct compaction priority Date: Tue, 6 Sep 2016 15:52:56 +0200 Message-Id: <20160906135258.18335-3-vbabka@suse.cz> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160906135258.18335-1-vbabka@suse.cz> References: <20160906135258.18335-1-vbabka@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During reclaim/compaction loop, compaction priority can be increased by the should_compact_retry() function, but the current code is not optimal. Priority is only increased when compaction_failed() is true, which means that compaction has scanned the whole zone. This may not happen even after multiple attempts with a lower priority due to parallel activity, so we might needlessly struggle on the lower priorities and possibly run out of compaction retry attempts in the process. After this patch we are guaranteed at least one attempt at the highest compaction priority even if we exhaust all retries at the lower priorities. Signed-off-by: Vlastimil Babka Cc: Michal Hocko Cc: Mel Gorman Cc: Joonsoo Kim Cc: David Rientjes Cc: Rik van Riel --- mm/page_alloc.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1df7694f4ec7..f8bed910e3cf 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3174,13 +3174,8 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, * so it doesn't really make much sense to retry except when the * failure could be caused by insufficient priority */ - if (compaction_failed(compact_result)) { - if (*compact_priority > MIN_COMPACT_PRIORITY) { - (*compact_priority)--; - return true; - } - return false; - } + if (compaction_failed(compact_result)) + goto check_priority; /* * make sure the compaction wasn't deferred or didn't bail out early @@ -3204,6 +3199,15 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, if (compaction_retries <= max_retries) return true; + /* + * Make sure there is at least one attempt at the highest priority + * if we exhausted all retries at the lower priorities + */ +check_priority: + if (*compact_priority > MIN_COMPACT_PRIORITY) { + (*compact_priority)--; + return true; + } return false; } #else -- 2.9.3