From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f181.google.com (mail-qc0-f181.google.com [209.85.216.181]) by kanga.kvack.org (Postfix) with ESMTP id A0D966B0035 for ; Tue, 6 May 2014 18:19:52 -0400 (EDT) Received: by mail-qc0-f181.google.com with SMTP id m20so165149qcx.12 for ; Tue, 06 May 2014 15:19:52 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTP id u7si3702003qab.236.2014.05.06.15.19.51 for ; Tue, 06 May 2014 15:19:52 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH 2/2] mm/compaction: avoid rescanning pageblocks in isolate_freepages Date: Tue, 6 May 2014 18:19:39 -0400 Message-Id: <53696008.4718e00a.3223.ffff8aa5SMTPIN_ADDED_BROKEN@mx.google.com> In-Reply-To: <1399044475-3154-1-git-send-email-vbabka@suse.cz> References: <5363B854.3010401@suse.cz> <1399044475-3154-1-git-send-email-vbabka@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: vbabka@suse.cz Cc: Andrew Morton , David Rientjes , Hugh Dickins , gthelen@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, Mel Gorman , iamjoonsoo.kim@lge.com, cl@linux.com, Rik van Riel On Fri, May 02, 2014 at 05:27:55PM +0200, Vlastimil Babka wrote: > 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: Naoya Horiguchi > Cc: Christoph Lameter > Cc: Rik van Riel > --- > mm/compaction.c | 18 ++++++------------ > 1 file changed, 6 insertions(+), 12 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 873d7de..1967850 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -686,12 +686,6 @@ 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. > @@ -731,19 +725,19 @@ 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; > - } Why don't you completely remove next_free_pfn and update cc->free_pfn directly? Thanks, Naoya Horiguchi -- 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