Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936882Ab3DJW2b (ORCPT ); Wed, 10 Apr 2013 18:28:31 -0400 Received: from rydia.net ([69.46.88.68]:52834 "EHLO mail.rydia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935439Ab3DJW2a (ORCPT ); Wed, 10 Apr 2013 18:28:30 -0400 Date: Wed, 10 Apr 2013 15:28:32 -0700 (PDT) From: dormando X-X-Sender: dormando@dtop To: Mel Gorman cc: Christoph Lameter , Andrew Morton , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , Johannes Weiner , Satoru Moriya , Michal Hocko , Linux-MM , LKML Subject: Re: [PATCH 0/10] Reduce system disruption due to kswapd V2 In-Reply-To: <20130410141445.GD3710@suse.de> Message-ID: References: <1365505625-9460-1-git-send-email-mgorman@suse.de> <0000013defd666bf-213d70fc-dfbd-4a50-82ed-e9f4f7391b55-000000@email.amazonses.com> <20130410141445.GD3710@suse.de> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1446 Lines: 31 > 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? -- 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/