From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753211Ab3LMPqE (ORCPT ); Fri, 13 Dec 2013 10:46:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:4628 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752460Ab3LMPqA (ORCPT ); Fri, 13 Dec 2013 10:46:00 -0500 Message-ID: <52AB2BAD.4080003@redhat.com> Date: Fri, 13 Dec 2013 10:45:49 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Mel Gorman CC: Johannes Weiner , Andrew Morton , Dave Hansen , Linux-MM , LKML 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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