From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755186Ab1HaLhr (ORCPT ); Wed, 31 Aug 2011 07:37:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1039 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754824Ab1HaLhq (ORCPT ); Wed, 31 Aug 2011 07:37:46 -0400 Date: Wed, 31 Aug 2011 13:37:10 +0200 From: Johannes Weiner To: Minchan Kim Cc: Andrew Morton , linux-mm , LKML , Mel Gorman , Rik van Riel Subject: Re: [PATCH 3/3] compaction accouting fix Message-ID: <20110831113710.GC17512@redhat.com> References: <282a4531f23c5e35cfddf089f93559130b4bb660.1321112552.git.minchan.kim@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <282a4531f23c5e35cfddf089f93559130b4bb660.1321112552.git.minchan.kim@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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). 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.