From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f180.google.com (mail-wi0-f180.google.com [209.85.212.180]) by kanga.kvack.org (Postfix) with ESMTP id 76EC26B0031 for ; Thu, 10 Jul 2014 08:06:19 -0400 (EDT) Received: by mail-wi0-f180.google.com with SMTP id hi2so4401291wib.1 for ; Thu, 10 Jul 2014 05:06:19 -0700 (PDT) Received: from zene.cmpxchg.org (zene.cmpxchg.org. [2a01:238:4224:fa00:ca1f:9ef3:caee:a2bd]) by mx.google.com with ESMTPS id dq8si12366880wid.17.2014.07.10.05.06.18 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 10 Jul 2014 05:06:18 -0700 (PDT) Date: Thu, 10 Jul 2014 08:06:15 -0400 From: Johannes Weiner Subject: Re: [PATCH 2/6] mm: Rearrange zone fields into read-only, page alloc, statistics and page reclaim lines Message-ID: <20140710120615.GJ29639@cmpxchg.org> References: <1404893588-21371-1-git-send-email-mgorman@suse.de> <1404893588-21371-3-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1404893588-21371-3-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , Linux Kernel , Linux-MM , Linux-FSDevel On Wed, Jul 09, 2014 at 09:13:04AM +0100, Mel Gorman wrote: > The arrangement of struct zone has changed over time and now it has reached the > point where there is some inappropriate sharing going on. On x86-64 for example > > o The zone->node field is shared with the zone lock and zone->node is accessed > frequently from the page allocator due to the fair zone allocation policy. > o span_seqlock is almost never used by shares a line with free_area > o Some zone statistics share a cache line with the LRU lock so reclaim-intensive > and allocator-intensive workloads can bounce the cache line on a stat update > > This patch rearranges struct zone to put read-only and read-mostly fields > together and then splits the page allocator intensive fields, the zone > statistics and the page reclaim intensive fields into their own cache > lines. Note that the type of lowmem_reserve changes due to the watermark > calculations being signed and avoiding a signed/unsigned conversion there. > > On the test configuration I used the overall size of struct zone shrunk > by one cache line. On smaller machines, this is not likely to be noticable. > However, on a 4-node NUMA machine running tiobench the system CPU overhead > is reduced by this patch. > > 3.16.0-rc3 3.16.0-rc3 > vanillarearrange-v5r9 > User 746.94 759.78 > System 65336.22 58350.98 > Elapsed 27553.52 27282.02 > > Signed-off-by: Mel Gorman Acked-by: Johannes Weiner -- 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