Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753730AbdC2PuC (ORCPT ); Wed, 29 Mar 2017 11:50:02 -0400 Received: from mx2.suse.de ([195.135.220.15]:45555 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753476AbdC2PuA (ORCPT ); Wed, 29 Mar 2017 11:50:00 -0400 Subject: Re: [PATCH v3 4/8] mm, page_alloc: count movable pages when stealing from pageblock To: Joonsoo Kim References: <20170307131545.28577-1-vbabka@suse.cz> <20170307131545.28577-5-vbabka@suse.cz> <20170316015323.GB14063@js1304-P5Q-DELUXE> Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Mel Gorman , David Rientjes , kernel-team@fb.com, kernel-team@lge.com From: Vlastimil Babka Message-ID: <0da9d0e1-59f3-79f2-2bc4-6c381f103813@suse.cz> Date: Wed, 29 Mar 2017 17:49:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170316015323.GB14063@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1614 Lines: 33 On 03/16/2017 02:53 AM, Joonsoo Kim wrote: > On Tue, Mar 07, 2017 at 02:15:41PM +0100, Vlastimil Babka wrote: >> When stealing pages from pageblock of a different migratetype, we count how >> many free pages were stolen, and change the pageblock's migratetype if more >> than half of the pageblock was free. This might be too conservative, as there >> might be other pages that are not free, but were allocated with the same >> migratetype as our allocation requested. > > I think that too conservative is good for movable case. In my experiments, > fragmentation spreads out when unmovable/reclaimable pageblock is > changed to movable pageblock prematurely ('prematurely' means that > allocated unmovable pages remains). As you said below, movable allocations > falling back to other pageblocks don't causes permanent fragmentation. > Therefore, we don't need to be less conservative for movable > allocation. So, how about following change to keep the criteria for > movable allocation conservative even with this counting improvement? > > threshold = (1 << (pageblock_order - 1)); > if (start_type == MIGRATE_MOVABLE) > threshold += (1 << (pageblock_order - 2)); > > if (free_pages + alike_pages >= threshold) > ... That could help, or also not. Keeping more pageblocks marked as unmovable also means that more unmovable allocations will spread out to them all, even if they would fit within less pageblocks. MIGRATE_MIXED was an idea to help in this case, as truly unmovable pageblocks would be preferred to the mixed ones. Can't decide about such change without testing :/ > Thanks. >