From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753230AbaGJMJD (ORCPT ); Thu, 10 Jul 2014 08:09:03 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:53082 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752173AbaGJMJB (ORCPT ); Thu, 10 Jul 2014 08:09:01 -0400 Date: Thu, 10 Jul 2014 08:08:57 -0400 From: Johannes Weiner To: Mel Gorman Cc: Andrew Morton , Linux Kernel , Linux-MM , Linux-FSDevel Subject: Re: [PATCH 3/6] mm: Move zone->pages_scanned into a vmstat counter Message-ID: <20140710120857.GK29639@cmpxchg.org> References: <1404893588-21371-1-git-send-email-mgorman@suse.de> <1404893588-21371-4-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1404893588-21371-4-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 09, 2014 at 09:13:05AM +0100, Mel Gorman wrote: > zone->pages_scanned is a write-intensive cache line during page reclaim > and it's also updated during page free. Move the counter into vmstat to > take advantage of the per-cpu updates and do not update it in the free > paths unless necessary. > > On a small UMA machine running tiobench the difference is marginal. On a > 4-node machine the overhead is more noticable. Note that automatic NUMA > balancing was disabled for this test as otherwise the system CPU overhead > is unpredictable. > > 3.16.0-rc3 3.16.0-rc3 3.16.0-rc3 > vanillarearrange-v5 vmstat-v5 > User 746.94 759.78 774.56 > System 65336.22 58350.98 32847.27 > Elapsed 27553.52 27282.02 27415.04 > > Note that the overhead reduction will vary depending on where exactly > pages are allocated and freed. > > Signed-off-by: Mel Gorman Acked-by: Johannes Weiner