From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by kanga.kvack.org (Postfix) with ESMTP id 3C7666B0253 for ; Wed, 29 Jul 2015 05:59:24 -0400 (EDT) Received: by wicmv11 with SMTP id mv11so211979517wic.0 for ; Wed, 29 Jul 2015 02:59:23 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id ja14si26134390wic.18.2015.07.29.02.59.22 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 29 Jul 2015 02:59:22 -0700 (PDT) Subject: Re: [PATCH 08/10] mm, page_alloc: Remove MIGRATE_RESERVE References: <1437379219-9160-1-git-send-email-mgorman@suse.com> <1437379219-9160-9-git-send-email-mgorman@suse.com> From: Vlastimil Babka Message-ID: <55B8A3F3.6090107@suse.cz> Date: Wed, 29 Jul 2015 11:59:15 +0200 MIME-Version: 1.0 In-Reply-To: <1437379219-9160-9-git-send-email-mgorman@suse.com> Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Linux-MM Cc: Johannes Weiner , Rik van Riel , Pintu Kumar , Xishi Qiu , Gioh Kim , LKML , Mel Gorman On 07/20/2015 10:00 AM, Mel Gorman wrote: > From: Mel Gorman > > MIGRATE_RESERVE preserves an old property of the buddy allocator that existed > prior to fragmentation avoidance -- min_free_kbytes worth of pages tended to > remain free until the only alternative was to fail the allocation. At the ^ I think you meant contiguous instead of free? Is it because splitting chooses lowest possible order, and grouping by mobility means you might be splitting e.g. order-5 movable page instead of using order-0 unmovable page? And that the fallback heuristics specifically select highest available order? I think it's not that obvious, so worth mentioning. > time it was discovered that high-order atomic allocations relied on this > property so MIGRATE_RESERVE was introduced. A later patch will introduce > an alternative MIGRATE_HIGHATOMIC so this patch deletes MIGRATE_RESERVE > and supporting code so it'll be easier to review. Note that this patch > in isolation may look like a false regression if someone was bisecting > high-order atomic allocation failures. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka -- 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