From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751520Ab3LKSYt (ORCPT ); Wed, 11 Dec 2013 13:24:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52819 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339Ab3LKSYq (ORCPT ); Wed, 11 Dec 2013 13:24:46 -0500 Message-ID: <52A8ADE4.8020609@redhat.com> Date: Wed, 11 Dec 2013 13:24:36 -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: Johannes Weiner CC: Andrew Morton , Dave Hansen , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch] mm: page_alloc: exclude unreclaimable allocations from zone fairness policy References: <1386785356-19911-1-git-send-email-hannes@cmpxchg.org> In-Reply-To: <1386785356-19911-1-git-send-email-hannes@cmpxchg.org> 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 12/11/2013 01:09 PM, Johannes Weiner wrote: > 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. > > Bisected-by: Dave Hansen > Signed-off-by: Johannes Weiner > Cc: Reviewed-by: Rik van Riel -- All rights reversed