Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753240AbaFWIgL (ORCPT ); Mon, 23 Jun 2014 04:36:11 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:55659 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752698AbaFWIca (ORCPT ); Mon, 23 Jun 2014 04:32:30 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Vlastimil Babka , Mel Gorman , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Dongjun Shin , Sunghwan Yun , Andrew Morton , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 012/111] mm/compaction: make isolate_freepages start at pageblock boundary Date: Mon, 23 Jun 2014 10:30:47 +0200 Message-Id: <4ce1386883095638c80190a37677b978e9650365.1403512280.git.jslaby@suse.cz> X-Mailer: git-send-email 2.0.0 In-Reply-To: <55d5f044a1fc96a74e4470e318c0a24f27a9ab7e.1403512280.git.jslaby@suse.cz> References: <55d5f044a1fc96a74e4470e318c0a24f27a9ab7e.1403512280.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vlastimil Babka 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 49e068f0b73dd042c186ffa9b420a9943e90389a upstream. The compaction freepage scanner implementation in isolate_freepages() starts by taking the current cc->free_pfn value as the first pfn. In a for loop, it scans from this first pfn to the end of the pageblock, and then subtracts pageblock_nr_pages from the first pfn to obtain the first pfn for the next for loop iteration. This means that when cc->free_pfn starts at offset X rather than being aligned on pageblock boundary, the scanner will start at offset X in all scanned pageblock, ignoring potentially many free pages. Currently this can happen when a) zone's end pfn is not pageblock aligned, or b) through zone->compact_cached_free_pfn with CONFIG_HOLES_IN_ZONE enabled and a hole spanning the beginning of a pageblock This patch fixes the problem by aligning the initial pfn in isolate_freepages() to pageblock boundary. This also permits replacing the end-of-pageblock alignment within the for loop with a simple pageblock_nr_pages increment. Signed-off-by: Vlastimil Babka Reported-by: Heesub Shin Acked-by: Minchan Kim Cc: Mel Gorman Acked-by: Joonsoo Kim Cc: Bartlomiej Zolnierkiewicz Cc: Michal Nazarewicz Cc: Naoya Horiguchi Cc: Christoph Lameter Acked-by: Rik van Riel Cc: Dongjun Shin Cc: Sunghwan Yun Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- mm/compaction.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 2b01acee43cd..6441083e76d3 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -657,16 +657,20 @@ static void isolate_freepages(struct zone *zone, struct compact_control *cc) { struct page *page; - unsigned long high_pfn, low_pfn, pfn, z_end_pfn, end_pfn; + unsigned long high_pfn, low_pfn, pfn, z_end_pfn; int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; /* * Initialise the free scanner. The starting point is where we last - * scanned from (or the end of the zone if starting). The low point - * is the end of the pageblock the migration scanner is using. + * 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 low boundary is the end of the pageblock the migration scanner + * is using. */ - pfn = cc->free_pfn; + pfn = cc->free_pfn & ~(pageblock_nr_pages-1); low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); /* @@ -686,6 +690,7 @@ static void isolate_freepages(struct zone *zone, for (; pfn >= low_pfn && cc->nr_migratepages > nr_freepages; pfn -= pageblock_nr_pages) { unsigned long isolated; + unsigned long end_pfn; /* * This can iterate a massively long zone without finding any @@ -720,13 +725,10 @@ static void isolate_freepages(struct zone *zone, isolated = 0; /* - * As pfn may not start aligned, pfn+pageblock_nr_page - * may cross a MAX_ORDER_NR_PAGES boundary and miss - * a pfn_valid check. Ensure isolate_freepages_block() - * only scans within a pageblock + * Take care when isolating in last pageblock of a zone which + * ends in the middle of a pageblock. */ - end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); - end_pfn = min(end_pfn, z_end_pfn); + end_pfn = min(pfn + pageblock_nr_pages, z_end_pfn); isolated = isolate_freepages_block(cc, pfn, end_pfn, freelist, false); nr_freepages += isolated; -- 2.0.0 -- 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/