From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 7BB0C6B0083 for ; Tue, 9 Jun 2009 22:14:19 -0400 (EDT) Date: Wed, 10 Jun 2009 10:14:40 +0800 From: Wu Fengguang Subject: Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA Message-ID: <20090610021440.GB6597@localhost> References: <1244466090-10711-1-git-send-email-mel@csn.ul.ie> <1244466090-10711-2-git-send-email-mel@csn.ul.ie> <20090609015822.GA6740@localhost> <20090609081424.GD18380@csn.ul.ie> <20090609082539.GA6897@localhost> <20090609083153.GG18380@csn.ul.ie> <20090609090735.GC7108@localhost> <20090609094050.GL18380@csn.ul.ie> <20090609133804.GB6583@localhost> <20090609150619.GT18380@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090609150619.GT18380@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: KOSAKI Motohiro , Rik van Riel , Christoph Lameter , "Zhang, Yanmin" , "linuxram@us.ibm.com" , linux-mm , LKML List-ID: On Tue, Jun 09, 2009 at 11:06:19PM +0800, Mel Gorman wrote: > On Tue, Jun 09, 2009 at 09:38:04PM +0800, Wu Fengguang wrote: > > On Tue, Jun 09, 2009 at 05:40:50PM +0800, Mel Gorman wrote: > > > > > > Conceivably though, zone_reclaim_interval could automatically tune > > > itself based on a heuristic like this if the administrator does not give > > > a specific value. I think that would be an interesting follow on once > > > we've brought back zone_reclaim_interval and get a feeling for how often > > > it is actually used. > > > > Well I don't think that's good practice. There are heuristic > > calculations all over the kernel. Shall we exporting parameters to > > user space just because we are not absolutely sure? Or shall we ship > > the heuristics and do adjustments based on feedbacks and only export > > parameters when we find _known cases_ that cannot be covered by pure > > heuristics? > > > > Good question - I don't have a satisfactory answer but I intuitively find > the zone_reclaim_interval easier to deal with than the heuristic. That said, > I would prefer if neither was required. Yes - can we rely on the (improved) accounting to make our "failure feedback" patches unnecessary? :) Thanks, Fengguang > In the patchset, I've added a counter for the number of times that the > scan-avoidance heuristic fails. If the tmpfs problem has been resolved > (patch with bug reporter, am awaiting test), I'll drop zone_reclaim_interval > altogether and we'll use the counter to detect if/when this situation > occurs again. -- 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