Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752467AbbFYS45 (ORCPT ); Thu, 25 Jun 2015 14:56:57 -0400 Received: from cantor2.suse.de ([195.135.220.15]:40529 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751766AbbFYS4v (ORCPT ); Thu, 25 Jun 2015 14:56:51 -0400 Message-ID: <558C4EF0.2010603@suse.cz> Date: Thu, 25 Jun 2015 20:56:48 +0200 From: Vlastimil Babka User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Joonsoo Kim , Mel Gorman CC: Joonsoo Kim , Andrew Morton , LKML , Linux Memory Management List , Rik van Riel , David Rientjes , Minchan Kim Subject: Re: [RFC PATCH 00/10] redesign compaction algorithm References: <1435193121-25880-1-git-send-email-iamjoonsoo.kim@lge.com> <20150625110314.GJ11809@suse.de> <20150625172550.GA26927@suse.de> 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: 1543 Lines: 26 On 25.6.2015 20:14, Joonsoo Kim wrote: >> The long-term success rate of fragmentation avoidance depends on >> > minimsing the number of UNMOVABLE allocation requests that use a >> > pageblock belonging to another migratetype. Once such a fallback occurs, >> > that pageblock potentially can never be used for a THP allocation again. >> > >> > Lets say there is an unmovable pageblock with 500 free pages in it. If >> > the freepage scanner uses that pageblock and allocates all 500 free >> > pages then the next unmovable allocation request needs a new pageblock. >> > If one is not completely free then it will fallback to using a >> > RECLAIMABLE or MOVABLE pageblock forever contaminating it. > Yes, I can imagine that situation. But, as I said above, we already use > non-movable pageblock for migration scanner. While unmovable > pageblock with 500 free pages fills, some other unmovable pageblock > with some movable pages will be emptied. Number of freepage > on non-movable would be maintained so fallback doesn't happen. There's nothing that guarantees that the migration scanner will be emptying unmovable pageblock, or am I missing something? Worse, those pageblocks would be marked to skip by the free scanner if it isolated free pages from them, so migration scanner would skip them. -- 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/