Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752773Ab3DKUNW (ORCPT ); Thu, 11 Apr 2013 16:13:22 -0400 Received: from mail-ea0-f171.google.com ([209.85.215.171]:41633 "EHLO mail-ea0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973Ab3DKUNU (ORCPT ); Thu, 11 Apr 2013 16:13:20 -0400 Date: Thu, 11 Apr 2013 22:13:16 +0200 From: Michal Hocko To: Mel Gorman Cc: dormando , Christoph Lameter , Andrew Morton , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , Johannes Weiner , Satoru Moriya , Linux-MM , LKML Subject: Re: [PATCH 0/10] Reduce system disruption due to kswapd V2 Message-ID: <20130411201316.GB15238@dhcp22.suse.cz> References: <1365505625-9460-1-git-send-email-mgorman@suse.de> <0000013defd666bf-213d70fc-dfbd-4a50-82ed-e9f4f7391b55-000000@email.amazonses.com> <20130410141445.GD3710@suse.de> <20130411091044.GG3710@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130411091044.GG3710@suse.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1932 Lines: 45 On Thu 11-04-13 10:10:44, Mel Gorman wrote: > On Wed, Apr 10, 2013 at 03:28:32PM -0700, dormando wrote: > > > On Tue, Apr 09, 2013 at 05:27:18PM +0000, Christoph Lameter wrote: > > > > One additional measure that may be useful is to make kswapd prefer one > > > > specific processor on a socket. Two benefits arise from that: > > > > > > > > 1. Better use of cpu caches and therefore higher speed, less > > > > serialization. > > > > > > > > > > Considering the volume of pages that kswapd can scan when it's active > > > I would expect that it trashes its cache anyway. The L1 cache would be > > > flushed after scanning struct pages for just a few MB of memory. > > > > > > > 2. Reduction of the disturbances to one processor. > > > > > > > > > > I've never checked it but I would have expected kswapd to stay on the > > > same processor for significant periods of time. Have you experienced > > > problems where kswapd bounces around on CPUs within a node causing > > > workload disruption? > > > > When kswapd shares the same CPU as our main process it causes a measurable > > drop in response time (graphs show tiny spikes at the same time memory is > > freed). Would be nice to be able to ensure it runs on a different core > > than our latency sensitive processes at least. We can pin processes to > > subsets of cores but I don't think there's a way to keep kswapd from > > waking up on any of them? > > I've never tried it myself but does the following work? > > taskset -p MASK `pidof kswapd` I would use pgrep rather than pidof which seem to need the whole process name but yes this should work as kswapdN is not PF_THREAD_BOUND kernel thread. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/