From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755923Ab1HaO5B (ORCPT ); Wed, 31 Aug 2011 10:57:01 -0400 Received: from mail-gw0-f46.google.com ([74.125.83.46]:55643 "EHLO mail-gw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755745Ab1HaO47 (ORCPT ); Wed, 31 Aug 2011 10:56:59 -0400 Date: Wed, 31 Aug 2011 23:56:51 +0900 From: Minchan Kim To: Johannes Weiner Cc: Andrew Morton , linux-mm , LKML , Mel Gorman , Rik van Riel Subject: Re: [PATCH 3/3] compaction accouting fix Message-ID: <20110831145651.GA2198@barrios-desktop> References: <282a4531f23c5e35cfddf089f93559130b4bb660.1321112552.git.minchan.kim@gmail.com> <20110831113710.GC17512@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110831113710.GC17512@redhat.com> 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 Wed, Aug 31, 2011 at 01:37:10PM +0200, Johannes Weiner wrote: > On Sun, Nov 13, 2011 at 01:37:43AM +0900, Minchan Kim wrote: > > I saw the following accouting of compaction during test of the series. > > > > compact_blocks_moved 251 > > compact_pages_moved 44 > > > > It's very awkward to me although it's possbile because it means we try to compact 251 blocks > > but it just migrated 44 pages. As further investigation, I found isolate_migratepages doesn't > > isolate any pages but it returns ISOLATE_SUCCESS and then, it just increases compact_blocks_moved > > but doesn't increased compact_pages_moved. > > > > This patch makes accouting of compaction works only in case of success of isolation. > > > > CC: Mel Gorman > > CC: Johannes Weiner > > CC: Rik van Riel > > Signed-off-by: Minchan Kim > > Acked-by: Johannes Weiner Thanks, Hannes. > > It's a teensy-bit awkward that isolate_migratepages() can return > success without actually isolating any new pages, just because there > are still some pages left from a previous run (cc->nr_migratepages is > maintained across isolation calls). If migrate_pages fails, we reset cc->nr_migratepages to zero in compact_zone. Am I missing something? > > Maybe isolate_migratepages() should just return an error if compaction > should really be aborted and 0 otherwise, and have compact_zone() > always check for cc->nr_migratepages itself? > > if (isolate_migratepages(zone, cc) < 0) { > ret = COMPACT_PARTIAL; > goto out; > } > > if (!cc->nr_migratepages) > continue; > > ... > > Just a nit-pick, though. If you don't agree, just leave it as is. -- Kind regards, Minchan Kim