From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760292AbaGYM2I (ORCPT ); Fri, 25 Jul 2014 08:28:08 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39935 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751916AbaGYM2G (ORCPT ); Fri, 25 Jul 2014 08:28:06 -0400 Date: Fri, 25 Jul 2014 13:28:01 +0100 From: Mel Gorman To: Vlastimil Babka Cc: linux-mm@kvack.org, Andrew Morton , David Rientjes , linux-kernel@vger.kernel.org, Minchan Kim , Joonsoo Kim , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel , Zhang Yanfei Subject: Re: [PATCH V4 05/15] mm, compaction: move pageblock checks up from isolate_migratepages_range() Message-ID: <20140725122801.GZ10819@suse.de> References: <1405518503-27687-1-git-send-email-vbabka@suse.cz> <1405518503-27687-6-git-send-email-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1405518503-27687-6-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 Wed, Jul 16, 2014 at 03:48:13PM +0200, Vlastimil Babka wrote: > isolate_migratepages_range() is the main function of the compaction scanner, > called either on a single pageblock by isolate_migratepages() during regular > compaction, or on an arbitrary range by CMA's __alloc_contig_migrate_range(). > It currently perfoms two pageblock-wide compaction suitability checks, and > because of the CMA callpath, it tracks if it crossed a pageblock boundary in > order to repeat those checks. > > However, closer inspection shows that those checks are always true for CMA: > - isolation_suitable() is true because CMA sets cc->ignore_skip_hint to true > - migrate_async_suitable() check is skipped because CMA uses sync compaction > > We can therefore move the compaction-specific checks to isolate_migratepages() > and simplify isolate_migratepages_range(). Furthermore, we can mimic the > freepage scanner family of functions, which has isolate_freepages_block() > function called both by compaction from isolate_freepages() and by CMA from > isolate_freepages_range(), where each use-case adds own specific glue code. > This allows further code simplification. > > Therefore, we rename isolate_migratepages_range() to isolate_freepages_block() > and limit its functionality to a single pageblock (or its subset). For CMA, > a new different isolate_migratepages_range() is created as a CMA-specific > wrapper for the _block() function. The checks specific to compaction are moved > to isolate_migratepages(). As part of the unification of these two families of > functions, we remove the redundant zone parameter where applicable, since zone > pointer is already passed in cc->zone. > > Furthermore, going back to compact_zone() and compact_finished() when pageblock > is found unsuitable (now by isolate_migratepages()) is wasteful - the checks > are meant to skip pageblocks quickly. The patch therefore also introduces a > simple loop into isolate_migratepages() so that it does not return immediately > on failed pageblock checks, but keeps going until isolate_migratepages_range() > gets called once. Similarily to isolate_freepages(), the function periodically > checks if it needs to reschedule or abort async compaction. > > Signed-off-by: Vlastimil Babka > Cc: Minchan Kim > Cc: Mel Gorman > Cc: Joonsoo Kim > Cc: Michal Nazarewicz > Cc: Naoya Horiguchi > Cc: Christoph Lameter > Cc: Rik van Riel > Cc: David Rientjes Acked-by: Mel Gorman -- Mel Gorman SUSE Labs