From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f53.google.com (mail-ee0-f53.google.com [74.125.83.53]) by kanga.kvack.org (Postfix) with ESMTP id B58E66B0031 for ; Wed, 11 Dec 2013 13:24:45 -0500 (EST) Received: by mail-ee0-f53.google.com with SMTP id b57so3087454eek.40 for ; Wed, 11 Dec 2013 10:24:45 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTP id r9si20333388eeo.107.2013.12.11.10.24.44 for ; Wed, 11 Dec 2013 10:24:44 -0800 (PST) Message-ID: <52A8ADE4.8020609@redhat.com> Date: Wed, 11 Dec 2013 13:24:36 -0500 From: Rik van Riel MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Dave Hansen , Mel Gorman , linux-mm@kvack.org, 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 -- 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