From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755904AbaEGMJh (ORCPT ); Wed, 7 May 2014 08:09:37 -0400 Received: from cantor2.suse.de ([195.135.220.15]:60159 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750933AbaEGMJe (ORCPT ); Wed, 7 May 2014 08:09:34 -0400 From: Vlastimil Babka To: Andrew Morton , David Rientjes Cc: Hugh Dickins , Greg Thelen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , Minchan Kim , Mel Gorman , Joonsoo Kim , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel Subject: [PATCH v2 2/2] mm/compaction: avoid rescanning pageblocks in isolate_freepages Date: Wed, 7 May 2014 14:09:10 +0200 Message-Id: <1399464550-26447-2-git-send-email-vbabka@suse.cz> X-Mailer: git-send-email 1.8.4.5 In-Reply-To: <1399464550-26447-1-git-send-email-vbabka@suse.cz> References: <1399464550-26447-1-git-send-email-vbabka@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The compaction free scanner in isolate_freepages() currently remembers PFN of the highest pageblock where it successfully isolates, to be used as the starting pageblock for the next invocation. The rationale behind this is that page migration might return free pages to the allocator when migration fails and we don't want to skip them if the compaction continues. Since migration now returns free pages back to compaction code where they can be reused, this is no longer a concern. This patch changes isolate_freepages() so that the PFN for restarting is updated with each pageblock where isolation is attempted. Using stress-highalloc from mmtests, this resulted in 10% reduction of the pages scanned by the free scanner. Note that the somewhat similar functionality that records highest successful pageblock in zone->compact_cached_free_pfn, remains unchanged. This cache is used when the whole compaction is restarted, not for multiple invocations of the free scanner during single compaction. Signed-off-by: Vlastimil Babka Cc: Minchan Kim Cc: Mel Gorman Cc: Joonsoo Kim Cc: Bartlomiej Zolnierkiewicz Cc: Michal Nazarewicz Cc: Naoya Horiguchi Cc: Christoph Lameter Cc: Rik van Riel --- v2: no changes, just keep patches together mm/compaction.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 383d562..83ca6f9 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -706,12 +706,6 @@ static void isolate_freepages(struct zone *zone, low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); /* - * If no pages are isolated, the block_start_pfn < low_pfn check - * will kick in. - */ - next_free_pfn = 0; - - /* * Isolate free pages until enough are available to migrate the * pages on cc->migratepages. We stop searching if the migrate * and free page scanners meet or enough free pages are isolated. @@ -751,19 +745,19 @@ static void isolate_freepages(struct zone *zone, continue; /* Found a block suitable for isolating free pages from */ + next_free_pfn = block_start_pfn; isolated = isolate_freepages_block(cc, block_start_pfn, block_end_pfn, freelist, false); nr_freepages += isolated; /* - * Record the highest PFN we isolated pages from. When next - * looking for free pages, the search will restart here as - * page migration may have returned some pages to the allocator + * Set a flag that we successfully isolated in this pageblock. + * In the next loop iteration, zone->compact_cached_free_pfn + * will not be updated and thus it will effectively contain the + * highest pageblock we isolated pages from. */ - if (isolated && next_free_pfn == 0) { + if (isolated) cc->finished_update_free = true; - next_free_pfn = block_start_pfn; - } } /* split_free_page does not map the pages */ -- 1.8.4.5 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f44.google.com (mail-ee0-f44.google.com [74.125.83.44]) by kanga.kvack.org (Postfix) with ESMTP id CD9616B0036 for ; Wed, 7 May 2014 08:09:35 -0400 (EDT) Received: by mail-ee0-f44.google.com with SMTP id c41so662293eek.31 for ; Wed, 07 May 2014 05:09:35 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id v41si16177236eew.134.2014.05.07.05.09.34 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 07 May 2014 05:09:34 -0700 (PDT) From: Vlastimil Babka Subject: [PATCH v2 2/2] mm/compaction: avoid rescanning pageblocks in isolate_freepages Date: Wed, 7 May 2014 14:09:10 +0200 Message-Id: <1399464550-26447-2-git-send-email-vbabka@suse.cz> In-Reply-To: <1399464550-26447-1-git-send-email-vbabka@suse.cz> References: <1399464550-26447-1-git-send-email-vbabka@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , David Rientjes Cc: Hugh Dickins , Greg Thelen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , Minchan Kim , Mel Gorman , Joonsoo Kim , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel The compaction free scanner in isolate_freepages() currently remembers PFN of the highest pageblock where it successfully isolates, to be used as the starting pageblock for the next invocation. The rationale behind this is that page migration might return free pages to the allocator when migration fails and we don't want to skip them if the compaction continues. Since migration now returns free pages back to compaction code where they can be reused, this is no longer a concern. This patch changes isolate_freepages() so that the PFN for restarting is updated with each pageblock where isolation is attempted. Using stress-highalloc from mmtests, this resulted in 10% reduction of the pages scanned by the free scanner. Note that the somewhat similar functionality that records highest successful pageblock in zone->compact_cached_free_pfn, remains unchanged. This cache is used when the whole compaction is restarted, not for multiple invocations of the free scanner during single compaction. Signed-off-by: Vlastimil Babka Cc: Minchan Kim Cc: Mel Gorman Cc: Joonsoo Kim Cc: Bartlomiej Zolnierkiewicz Cc: Michal Nazarewicz Cc: Naoya Horiguchi Cc: Christoph Lameter Cc: Rik van Riel --- v2: no changes, just keep patches together mm/compaction.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 383d562..83ca6f9 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -706,12 +706,6 @@ static void isolate_freepages(struct zone *zone, low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); /* - * If no pages are isolated, the block_start_pfn < low_pfn check - * will kick in. - */ - next_free_pfn = 0; - - /* * Isolate free pages until enough are available to migrate the * pages on cc->migratepages. We stop searching if the migrate * and free page scanners meet or enough free pages are isolated. @@ -751,19 +745,19 @@ static void isolate_freepages(struct zone *zone, continue; /* Found a block suitable for isolating free pages from */ + next_free_pfn = block_start_pfn; isolated = isolate_freepages_block(cc, block_start_pfn, block_end_pfn, freelist, false); nr_freepages += isolated; /* - * Record the highest PFN we isolated pages from. When next - * looking for free pages, the search will restart here as - * page migration may have returned some pages to the allocator + * Set a flag that we successfully isolated in this pageblock. + * In the next loop iteration, zone->compact_cached_free_pfn + * will not be updated and thus it will effectively contain the + * highest pageblock we isolated pages from. */ - if (isolated && next_free_pfn == 0) { + if (isolated) cc->finished_update_free = true; - next_free_pfn = block_start_pfn; - } } /* split_free_page does not map the pages */ -- 1.8.4.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org