From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 2A8316B025E for ; Mon, 18 Jul 2016 05:12:57 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id f126so53803589wma.3 for ; Mon, 18 Jul 2016 02:12:57 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 78si13701800wmq.114.2016.07.18.02.12.55 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 18 Jul 2016 02:12:55 -0700 (PDT) Subject: Re: [PATCH v3 09/17] mm, compaction: make whole_zone flag ignore cached scanner positions References: <20160624095437.16385-1-vbabka@suse.cz> <20160624095437.16385-10-vbabka@suse.cz> <20160706050939.GD23627@js1304-P5Q-DELUXE> From: Vlastimil Babka Message-ID: <1c0e2da2-115e-d676-cfec-e572270789ca@suse.cz> Date: Mon, 18 Jul 2016 11:12:51 +0200 MIME-Version: 1.0 In-Reply-To: <20160706050939.GD23627@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Mel Gorman , David Rientjes , Rik van Riel On 07/06/2016 07:09 AM, Joonsoo Kim wrote: > On Fri, Jun 24, 2016 at 11:54:29AM +0200, Vlastimil Babka wrote: >> A recent patch has added whole_zone flag that compaction sets when scanning >> starts from the zone boundary, in order to report that zone has been fully >> scanned in one attempt. For allocations that want to try really hard or cannot >> fail, we will want to introduce a mode where scanning whole zone is guaranteed >> regardless of the cached positions. >> >> This patch reuses the whole_zone flag in a way that if it's already passed true >> to compaction, the cached scanner positions are ignored. Employing this flag > > Okay. But, please don't reset cached scanner position even if whole_zone > flag is set. Just set cc->migrate_pfn and free_pfn, appropriately. With Won't that result in confusion on cached position updates during compaction where it checks the previous cached position? I wonder what kinds of corner cases it can bring... > your following patches, whole_zone could be set without any compaction > try I don't understand what you mean here? Even after whole series, whole_zone is only checked, and positions thus reset, after passing the compaction_suitable() call from compact_zone(). So at that point we can say that compaction is being actually tried and it's not a drive-by reset? 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