From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com [209.85.212.176]) by kanga.kvack.org (Postfix) with ESMTP id 3526C6B00B3 for ; Fri, 13 Dec 2013 10:45:59 -0500 (EST) Received: by mail-wi0-f176.google.com with SMTP id hq4so1274825wib.9 for ; Fri, 13 Dec 2013 07:45:58 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTP id k1si973695wjz.126.2013.12.13.07.45.57 for ; Fri, 13 Dec 2013 07:45:58 -0800 (PST) Message-ID: <52AB2BAD.4080003@redhat.com> Date: Fri, 13 Dec 2013 10:45:49 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 1/7] mm: page_alloc: exclude unreclaimable allocations from zone fairness policy References: <1386943807-29601-1-git-send-email-mgorman@suse.de> <1386943807-29601-2-git-send-email-mgorman@suse.de> In-Reply-To: <1386943807-29601-2-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Johannes Weiner , Andrew Morton , Dave Hansen , Linux-MM , LKML On 12/13/2013 09:10 AM, Mel Gorman wrote: > From: Johannes Weiner > > Dave Hansen noted a regression in a microbenchmark that loops around > open() and close() on an 8-node NUMA machine and bisected it down to > 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy"). That > change forces the slab allocations of the file descriptor to spread > out to all 8 nodes, causing remote references in the page allocator > and slab. > > The round-robin policy is only there to provide fairness among memory > allocations that are reclaimed involuntarily based on pressure in each > zone. It does not make sense to apply it to unreclaimable kernel > allocations that are freed manually, in this case instantly after the > allocation, and incur the remote reference costs twice for no reason. > > Only round-robin allocations that are usually freed through page > reclaim or slab shrinking. > > Cc: > Bisected-by: Dave Hansen > Signed-off-by: Johannes Weiner > Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel -- All rights reversed -- 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