From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx151.postini.com [74.125.245.151]) by kanga.kvack.org (Postfix) with SMTP id 2FE576B0005 for ; Wed, 10 Apr 2013 18:28:31 -0400 (EDT) Date: Wed, 10 Apr 2013 15:28:32 -0700 (PDT) From: dormando 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: 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 > 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, 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