From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id 3F68C6B006C for ; Thu, 25 Jun 2015 14:56:52 -0400 (EDT) Received: by wgqq4 with SMTP id q4so70307470wgq.1 for ; Thu, 25 Jun 2015 11:56:51 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id r18si10196103wiv.5.2015.06.25.11.56.50 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 25 Jun 2015 11:56:50 -0700 (PDT) Message-ID: <558C4EF0.2010603@suse.cz> Date: Thu, 25 Jun 2015 20:56:48 +0200 From: Vlastimil Babka MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim , Mel Gorman Cc: Joonsoo Kim , Andrew Morton , LKML , Linux Memory Management List , Rik van Riel , David Rientjes , Minchan Kim 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, 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