Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933436AbbBBOH0 (ORCPT ); Mon, 2 Feb 2015 09:07:26 -0500 Received: from cantor2.suse.de ([195.135.220.15]:54371 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932206AbbBBOHW (ORCPT ); Mon, 2 Feb 2015 09:07:22 -0500 Message-ID: <54CF8495.8010602@suse.cz> Date: Mon, 02 Feb 2015 15:07:17 +0100 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Joonsoo Kim CC: Andrew Morton , Mel Gorman , David Rientjes , Rik van Riel , Linux Memory Management List , LKML , Zhang Yanfei , Joonsoo Kim Subject: Re: [RFC PATCH v3 3/3] mm/compaction: enhance compaction finish condition References: <1422861348-5117-1-git-send-email-iamjoonsoo.kim@lge.com> <1422861348-5117-3-git-send-email-iamjoonsoo.kim@lge.com> <54CF4F61.3070905@suse.cz> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1791 Lines: 37 On 02/02/2015 02:23 PM, Joonsoo Kim wrote: > 2015-02-02 19:20 GMT+09:00 Vlastimil Babka : >> On 02/02/2015 08:15 AM, Joonsoo Kim wrote: >> >> So I've realized that this problaby won't always work as intended :/ Because we >> still differ from what page allocator does. >> Consider we compact for UNMOVABLE allocation. First we try RECLAIMABLE fallback. >> Turns out we could fallback, but not steal, hence we skip it due to >> only_stealable == true. So we try MOVABLE, and turns out we can steal, so we >> finish compaction. >> Then the allocation attempt follows, and it will fallback to RECLAIMABLE, >> without extra stealing. The compaction decision for MOVABLE was moot. >> Is it a big problem? Probably not, the compaction will still perform some extra >> anti-fragmentation on average, but we should consider it. > > Hello, > > First of all, thanks for quick review. :) > > Hmm... I don't get it. Is this case possible in current implementation? > can_steal_fallback() decides whether steal is possible or not, based > on freepage order > and start_migratetype. If fallback freepage is on RECLAIMABLE and > MOVABLE type and > they are same order, can_steal could be true for both or false for > neither. If order is > different, compaction decision would be recognized by > __rmqueue_fallback() since it > try to find freepage from high order to low order. Ah, right, I got confused into thinking that the result of can_steal depends on how many freepages it found within the pageblock to steal. Sorry about the noise. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/