From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751161AbaDPBwe (ORCPT ); Tue, 15 Apr 2014 21:52:34 -0400 Received: from lgeamrelo04.lge.com ([156.147.1.127]:42974 "EHLO lgeamrelo04.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750898AbaDPBwd (ORCPT ); Tue, 15 Apr 2014 21:52:33 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Wed, 16 Apr 2014 10:52:59 +0900 From: Joonsoo Kim To: Vlastimil Babka Cc: Andrew Morton , Heesub Shin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dongjun Shin , Sunghwan Yun , Minchan Kim , Mel Gorman , Bartlomiej Zolnierkiewicz , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel Subject: Re: [PATCH 1/2] mm/compaction: make isolate_freepages start at pageblock boundary Message-ID: <20140416015259.GA17841@js1304-P5Q-DELUXE> References: <5342BA34.8050006@suse.cz> <1397553507-15330-1-git-send-email-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1397553507-15330-1-git-send-email-vbabka@suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 15, 2014 at 11:18:26AM +0200, Vlastimil Babka wrote: > 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 allows to replace 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 > 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 > --- > mm/compaction.c | 22 ++++++++++++---------- > 1 file changed, 12 insertions(+), 10 deletions(-) Acked-by: Joonsoo Kim