From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f171.google.com (mail-pd0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 802A76B0031 for ; Sun, 9 Feb 2014 19:41:15 -0500 (EST) Received: by mail-pd0-f171.google.com with SMTP id g10so5408829pdj.2 for ; Sun, 09 Feb 2014 16:41:15 -0800 (PST) Received: from LGEAMRELO01.lge.com (lgeamrelo01.lge.com. [156.147.1.125]) by mx.google.com with ESMTP id q5si13272765pae.85.2014.02.09.16.41.13 for ; Sun, 09 Feb 2014 16:41:14 -0800 (PST) Date: Mon, 10 Feb 2014 09:41:22 +0900 From: Joonsoo Kim Subject: Re: [PATCH 2/5] mm/compaction: do not call suitable_migration_target() on every page Message-ID: <20140210004122.GB12049@lge.com> References: <1391749726-28910-1-git-send-email-iamjoonsoo.kim@lge.com> <1391749726-28910-3-git-send-email-iamjoonsoo.kim@lge.com> <52F4A90D.20804@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52F4A90D.20804@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Andrew Morton , Mel Gorman , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri, Feb 07, 2014 at 10:36:13AM +0100, Vlastimil Babka wrote: > On 02/07/2014 06:08 AM, Joonsoo Kim wrote: > > suitable_migration_target() checks that pageblock is suitable for > > migration target. In isolate_freepages_block(), it is called on every > > page and this is inefficient. So make it called once per pageblock. > > Hmm but in sync compaction, compact_checklock_irqsave() may drop the zone->lock, > reschedule and reacquire it and thus possibly invalidate your previous check. Async > compaction is ok as that will quit immediately. So you could probably communicate that > this happened and invalidate checked_pageblock in such case. Or maybe this would not > happen too enough to worry about rare suboptimal migrations? So, the result of previous check can be changed only if *this* pageblock's migratetype is changed while we drop the lock. I guess that this is really rare event, and, in this case, this pageblock already has mixed migratetype pages, so it has no serious problem. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org