Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754753AbaFWJRl (ORCPT ); Mon, 23 Jun 2014 05:17:41 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:28944 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752007AbaFWJRj (ORCPT ); Mon, 23 Jun 2014 05:17:39 -0400 X-IronPort-AV: E=Sophos;i="5.00,759,1396972800"; d="scan'208";a="32279779" Message-ID: <53A7F0AA.2070000@cn.fujitsu.com> Date: Mon, 23 Jun 2014 17:17:30 +0800 From: Zhang Yanfei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131030 Thunderbird/17.0.10 MIME-Version: 1.0 To: Vlastimil Babka CC: , Andrew Morton , David Rientjes , Minchan Kim , Mel Gorman , Joonsoo Kim , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel , Subject: Re: [PATCH v3 08/13] mm, compaction: remember position within pageblock in free pages scanner References: <1403279383-5862-1-git-send-email-vbabka@suse.cz> <1403279383-5862-9-git-send-email-vbabka@suse.cz> In-Reply-To: <1403279383-5862-9-git-send-email-vbabka@suse.cz> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.225.89] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2014 11:49 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 > Acked-by: David Rientjes > Cc: Minchan Kim > Cc: Mel Gorman > Cc: Joonsoo Kim > Cc: Michal Nazarewicz > Cc: Naoya Horiguchi > Cc: Christoph Lameter > Cc: Rik van Riel > Cc: Zhang Yanfei Reviewed-by: Zhang Yanfei > --- > mm/compaction.c | 40 +++++++++++++++++++++++++++++++--------- > 1 file changed, 31 insertions(+), 9 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 9f6e857..41c7005 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -287,7 +287,7 @@ 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) > @@ -296,6 +296,7 @@ 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); > > @@ -369,6 +370,9 @@ isolate_fail: > break; > } > > + /* Record how far we have got within the block */ > + *start_pfn = blockpfn; > + > trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated); > > /* > @@ -413,6 +417,9 @@ 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; > > @@ -423,8 +430,8 @@ 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 > @@ -708,6 +715,7 @@ static void isolate_freepages(struct zone *zone, > { > struct page *page; > unsigned long block_start_pfn; /* start of current pageblock */ > + unsigned long isolate_start_pfn; /* exact pfn we start at */ > unsigned long block_end_pfn; /* end of current pageblock */ > unsigned long low_pfn; /* lowest pfn scanner is able to scan */ > int nr_freepages = cc->nr_freepages; > @@ -716,14 +724,15 @@ static void isolate_freepages(struct zone *zone, > /* > * Initialise the free scanner. The starting point is where we last > * successfully isolated from, zone-cached value, or the end of the > - * zone when isolating for the first time. We need this aligned to > - * the pageblock boundary, because we do > + * zone when isolating for the first time. For looping we also need > + * this pfn aligned down to the pageblock boundary, because we do > * block_start_pfn -= pageblock_nr_pages in the for loop. > * For ending point, take care when isolating in last pageblock of a > * a zone which ends in the middle of a pageblock. > * The low boundary is the end of the pageblock the migration scanner > * is using. > */ > + isolate_start_pfn = cc->free_pfn; > block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1); > block_end_pfn = min(block_start_pfn + pageblock_nr_pages, > zone_end_pfn(zone)); > @@ -736,7 +745,8 @@ static void isolate_freepages(struct zone *zone, > */ > for (; block_start_pfn >= low_pfn && cc->nr_migratepages > nr_freepages; > block_end_pfn = block_start_pfn, > - block_start_pfn -= pageblock_nr_pages) { > + block_start_pfn -= pageblock_nr_pages, > + isolate_start_pfn = block_start_pfn) { > unsigned long isolated; > > /* > @@ -770,13 +780,25 @@ static void isolate_freepages(struct zone *zone, > if (!isolation_suitable(cc, page)) > continue; > > - /* Found a block suitable for isolating free pages from */ > - cc->free_pfn = block_start_pfn; > - isolated = isolate_freepages_block(cc, block_start_pfn, > + /* Found a block suitable for isolating free pages from. */ > + 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, > + * which is where isolate_freepages_block() left off. > + * But if it scanned the whole pageblock, isolate_start_pfn > + * now points at block_end_pfn, which is the start of the next > + * pageblock. > + * In that case we will however want to restart at the start > + * of the previous pageblock. > + */ > + cc->free_pfn = (isolate_start_pfn < block_end_pfn) ? > + isolate_start_pfn : > + block_start_pfn - pageblock_nr_pages; > + > + /* > * 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 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/