From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f177.google.com (mail-pd0-f177.google.com [209.85.192.177]) by kanga.kvack.org (Postfix) with ESMTP id 95BE36B0140 for ; Tue, 10 Jun 2014 23:29:50 -0400 (EDT) Received: by mail-pd0-f177.google.com with SMTP id g10so6682003pdj.8 for ; Tue, 10 Jun 2014 20:29:50 -0700 (PDT) Received: from heian.cn.fujitsu.com ([59.151.112.132]) by mx.google.com with ESMTP id ys1si5060870pac.12.2014.06.10.20.29.47 for ; Tue, 10 Jun 2014 20:29:49 -0700 (PDT) Message-ID: <5397CD36.5040909@cn.fujitsu.com> Date: Wed, 11 Jun 2014 11:29:58 +0800 From: Zhang Yanfei MIME-Version: 1.0 Subject: Re: [PATCH 05/10] mm, compaction: remember position within pageblock in free pages scanner References: <1402305982-6928-1-git-send-email-vbabka@suse.cz> <1402305982-6928-5-git-send-email-vbabka@suse.cz> In-Reply-To: <1402305982-6928-5-git-send-email-vbabka@suse.cz> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Greg Thelen , Minchan Kim , Mel Gorman , Joonsoo Kim , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel On 06/09/2014 05:26 PM, Vlastimil Babka wrote: > Unlike the migration scanner, the free scanner remembers the beginning of the > last scanned pageblock in cc->free_pfn. It might be therefore rescanning pages > uselessly when called several times during single compaction. This might have > been useful when pages were returned to the buddy allocator after a failed > migration, but this is no longer the case. > > This patch changes the meaning of cc->free_pfn so that if it points to a > middle of a pageblock, that pageblock is scanned only from cc->free_pfn to the > end. isolate_freepages_block() will record the pfn of the last page it looked > at, which is then used to update cc->free_pfn. > > In the mmtests stress-highalloc benchmark, this has resulted in lowering the > ratio between pages scanned by both scanners, from 2.5 free pages per migrate > page, to 2.25 free pages per migrate page, without affecting success rates. > > Signed-off-by: Vlastimil Babka Reviewed-by: Zhang Yanfei > Cc: Minchan Kim > Cc: Mel Gorman > Cc: Joonsoo Kim > Cc: Michal Nazarewicz > Cc: Naoya Horiguchi > Cc: Christoph Lameter > Cc: Rik van Riel > Cc: David Rientjes > --- > mm/compaction.c | 33 ++++++++++++++++++++++++++++----- > 1 file changed, 28 insertions(+), 5 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 83f72bd..58dfaaa 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -297,7 +297,7 @@ static bool suitable_migration_target(struct page *page) > * (even though it may still end up isolating some pages). > */ > static unsigned long isolate_freepages_block(struct compact_control *cc, > - unsigned long blockpfn, > + unsigned long *start_pfn, > unsigned long end_pfn, > struct list_head *freelist, > bool strict) > @@ -306,6 +306,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > struct page *cursor, *valid_page = NULL; > unsigned long flags; > bool locked = false; > + unsigned long blockpfn = *start_pfn; > > cursor = pfn_to_page(blockpfn); > > @@ -314,6 +315,9 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > int isolated, i; > struct page *page = cursor; > > + /* Record how far we have got within the block */ > + *start_pfn = blockpfn; > + > /* > * Periodically drop the lock (if held) regardless of its > * contention, to give chance to IRQs. Abort async compaction > @@ -424,6 +428,9 @@ isolate_freepages_range(struct compact_control *cc, > LIST_HEAD(freelist); > > for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) { > + /* Protect pfn from changing by isolate_freepages_block */ > + unsigned long isolate_start_pfn = pfn; > + > if (!pfn_valid(pfn) || cc->zone != page_zone(pfn_to_page(pfn))) > break; > > @@ -434,8 +441,8 @@ isolate_freepages_range(struct compact_control *cc, > block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); > block_end_pfn = min(block_end_pfn, end_pfn); > > - isolated = isolate_freepages_block(cc, pfn, block_end_pfn, > - &freelist, true); > + isolated = isolate_freepages_block(cc, &isolate_start_pfn, > + block_end_pfn, &freelist, true); > > /* > * In strict mode, isolate_freepages_block() returns 0 if > @@ -774,6 +781,7 @@ static void isolate_freepages(struct zone *zone, > block_end_pfn = block_start_pfn, > block_start_pfn -= pageblock_nr_pages) { > unsigned long isolated; > + unsigned long isolate_start_pfn; > > /* > * This can iterate a massively long zone without finding any > @@ -807,12 +815,27 @@ static void isolate_freepages(struct zone *zone, > continue; > > /* Found a block suitable for isolating free pages from */ > - cc->free_pfn = block_start_pfn; > - isolated = isolate_freepages_block(cc, block_start_pfn, > + isolate_start_pfn = block_start_pfn; > + > + /* > + * If we are restarting the free scanner in this block, do not > + * rescan the beginning of the block > + */ > + if (cc->free_pfn < block_end_pfn) > + isolate_start_pfn = cc->free_pfn; > + > + isolated = isolate_freepages_block(cc, &isolate_start_pfn, > block_end_pfn, freelist, false); > nr_freepages += isolated; > > /* > + * Remember where the free scanner should restart next time. > + * This will point to the last page of pageblock we just > + * scanned, if we scanned it fully. > + */ > + cc->free_pfn = isolate_start_pfn; > + > + /* > * 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 > -- Thanks. Zhang Yanfei -- 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