From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756688AbaKSVLk (ORCPT ); Wed, 19 Nov 2014 16:11:40 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:57100 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756506AbaKSVLe (ORCPT ); Wed, 19 Nov 2014 16:11:34 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vlastimil Babka , Minchan Kim , Mel Gorman , Joonsoo Kim , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel , Dongjun Shin , Sunghwan Yun , Andrew Morton , Linus Torvalds Subject: [PATCH 3.14 108/122] mm/compaction: cleanup isolate_freepages() Date: Wed, 19 Nov 2014 12:52:38 -0800 Message-Id: <20141119205212.429950366@linuxfoundation.org> X-Mailer: git-send-email 2.1.3 In-Reply-To: <20141119205208.812884198@linuxfoundation.org> References: <20141119205208.812884198@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vlastimil Babka commit c96b9e508f3d06ddb601dcc9792d62c044ab359e upstream. isolate_freepages() is currently somewhat hard to follow thanks to many looks like it is related to the 'low_pfn' variable, but in fact it is not. This patch renames the 'high_pfn' variable to a hopefully less confusing name, and slightly changes its handling without a functional change. A comment made obsolete by recent changes is also updated. [akpm@linux-foundation.org: comment fixes, per Minchan] [iamjoonsoo.kim@lge.com: cleanups] 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 Cc: Dongjun Shin Cc: Sunghwan Yun Signed-off-by: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Greg Kroah-Hartman --- mm/compaction.c | 56 +++++++++++++++++++++++++++----------------------------- 1 file changed, 27 insertions(+), 29 deletions(-) --- a/mm/compaction.c +++ b/mm/compaction.c @@ -665,7 +665,10 @@ static void isolate_freepages(struct zon struct compact_control *cc) { struct page *page; - unsigned long high_pfn, low_pfn, pfn, z_end_pfn; + unsigned long block_start_pfn; /* start of current pageblock */ + unsigned long block_end_pfn; /* end of current pageblock */ + unsigned long low_pfn; /* lowest pfn scanner is able to scan */ + unsigned long next_free_pfn; /* start pfn for scaning at next round */ int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; @@ -673,32 +676,33 @@ static void isolate_freepages(struct zon * 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 pfn -= pageblock_nr_pages - * in the for loop. + * 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. */ - pfn = cc->free_pfn & ~(pageblock_nr_pages-1); + block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1); + block_end_pfn = min(block_start_pfn + pageblock_nr_pages, + zone_end_pfn(zone)); low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); /* - * Take care that if the migration scanner is at the end of the zone - * that the free scanner does not accidentally move to the next zone - * in the next isolation cycle. + * If no pages are isolated, the block_start_pfn < low_pfn check + * will kick in. */ - high_pfn = min(low_pfn, pfn); - - z_end_pfn = zone_end_pfn(zone); + 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. */ - for (; pfn >= low_pfn && cc->nr_migratepages > nr_freepages; - pfn -= pageblock_nr_pages) { + for (; block_start_pfn >= low_pfn && cc->nr_migratepages > nr_freepages; + block_end_pfn = block_start_pfn, + block_start_pfn -= pageblock_nr_pages) { unsigned long isolated; - unsigned long end_pfn; /* * This can iterate a massively long zone without finding any @@ -707,7 +711,7 @@ static void isolate_freepages(struct zon */ cond_resched(); - if (!pfn_valid(pfn)) + if (!pfn_valid(block_start_pfn)) continue; /* @@ -717,7 +721,7 @@ static void isolate_freepages(struct zon * i.e. it's possible that all pages within a zones range of * pages do not belong to a single zone. */ - page = pfn_to_page(pfn); + page = pfn_to_page(block_start_pfn); if (page_zone(page) != zone) continue; @@ -730,14 +734,8 @@ static void isolate_freepages(struct zon continue; /* Found a block suitable for isolating free pages from */ - - /* - * Take care when isolating in last pageblock of a zone which - * ends in the middle of a pageblock. - */ - end_pfn = min(pfn + pageblock_nr_pages, z_end_pfn); - isolated = isolate_freepages_block(cc, pfn, end_pfn, - freelist, false); + isolated = isolate_freepages_block(cc, block_start_pfn, + block_end_pfn, freelist, false); nr_freepages += isolated; /* @@ -745,9 +743,9 @@ static void isolate_freepages(struct zon * looking for free pages, the search will restart here as * page migration may have returned some pages to the allocator */ - if (isolated) { + if (isolated && next_free_pfn == 0) { cc->finished_update_free = true; - high_pfn = max(high_pfn, pfn); + next_free_pfn = block_start_pfn; } } @@ -758,10 +756,10 @@ static void isolate_freepages(struct zon * If we crossed the migrate scanner, we want to keep it that way * so that compact_finished() may detect this */ - if (pfn < low_pfn) - cc->free_pfn = max(pfn, zone->zone_start_pfn); - else - cc->free_pfn = high_pfn; + if (block_start_pfn < low_pfn) + next_free_pfn = cc->migrate_pfn; + + cc->free_pfn = next_free_pfn; cc->nr_freepages = nr_freepages; }