Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932677AbaLDRNT (ORCPT ); Thu, 4 Dec 2014 12:13:19 -0500 Received: from cantor2.suse.de ([195.135.220.15]:58016 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932466AbaLDRNR (ORCPT ); Thu, 4 Dec 2014 12:13:17 -0500 From: Vlastimil Babka To: linux-mm@kvack.org, Joonsoo Kim Cc: linux-kernel@vger.kernel.org, Minchan Kim , Mel Gorman , Rik van Riel , David Rientjes , Vlastimil Babka Subject: [RFC PATCH 2/3] mm: more aggressive page stealing for UNMOVABLE allocations Date: Thu, 4 Dec 2014 18:12:57 +0100 Message-Id: <1417713178-10256-3-git-send-email-vbabka@suse.cz> X-Mailer: git-send-email 2.1.2 In-Reply-To: <1417713178-10256-1-git-send-email-vbabka@suse.cz> References: <1417713178-10256-1-git-send-email-vbabka@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When allocation falls back to stealing free pages of another migratetype, it can decide to steal extra pages, or even the whole pageblock in order to reduce fragmentation, which could happen if further allocation fallbacks pick a different pageblock. In try_to_steal_freepages(), one of the situations where extra pages are stolen happens when we are trying to allocate a MIGRATE_RECLAIMABLE page. However, MIGRATE_UNMOVABLE allocations are not treated the same way, although spreading such allocation over multiple fallback pageblocks is arguably even worse than it is for RECLAIMABLE allocations. To minimize fragmentation, we should minimize the number of such fallbacks, and thus steal as much as is possible from each fallback pageblock. This patch thus adds a check for MIGRATE_UNMOVABLE to the decision to steal extra free pages. When evaluating with stress-highalloc from mmtests, this has reduced the number of MIGRATE_UNMOVABLE fallbacks to roughly 1/6. The number of these fallbacks stealing from MIGRATE_MOVABLE block is reduced to 1/3. Signed-off-by: Vlastimil Babka --- mm/page_alloc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 548b072..a14249c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1098,6 +1098,7 @@ static int try_to_steal_freepages(struct zone *zone, struct page *page, if (current_order >= pageblock_order / 2 || start_type == MIGRATE_RECLAIMABLE || + start_type == MIGRATE_UNMOVABLE || page_group_by_mobility_disabled) { int pages; -- 2.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/