From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx189.postini.com [74.125.245.189]) by kanga.kvack.org (Postfix) with SMTP id 743DA6B0005 for ; Thu, 11 Apr 2013 10:19:47 -0400 (EDT) Date: Thu, 11 Apr 2013 15:19:43 +0100 From: Mel Gorman Subject: Re: [PATCH] mm: Print the correct method to disable automatic numa migration Message-ID: <20130411141942.GL3710@suse.de> References: <1365622514-26614-1-git-send-email-andi@firstfloor.org> <20130411124803.GK3710@suse.de> <20130411140425.GJ16732@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130411140425.GJ16732@two.firstfloor.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andi Kleen Cc: akpm@linux-foundation.org, linux-mm@kvack.org, Andi Kleen On Thu, Apr 11, 2013 at 04:04:25PM +0200, Andi Kleen wrote: > > As David pointed out, CONFIG_NUMA_BALANCING_DEFAULT_ENABLED only comes > > into play when CONFIG_NUMA_BALANCING is set and CONFIG_NUMA_BALANCING > > will default to N for make oldconfig. I think it's sensible to enable it > > by default if it's configured in. > > I've got reports from users who got it unexpected and it messed > everything up for them. > They enabled the option to have the feature and were then surprised it was enabled? That surprises me. > > > > David has also already pointed out the problems with NO_NUMA vs -NUMA and > > the fact that the option only exists if CONFIG_SCHED_DEBUG which I agree > > is unfortunate. Ends up with this sort of mess > > We just need the sysctl. Are you adding one or should I send > another patch with it? > I hadn't planned on it in the short term at least. Originally there was a sysctl to control the NUMA auto balancing behaviour but it was one of the points of contention that got dropped along the way. As SCHED_DEBUG is enabled in some distribution configs at least, it was expected the option would generally be available even though the documentation for /sys/kernel/debug/sched_features is non-existent. I had hoped to have revisited NUMA balancing a long time ago but too many bugs have been getting in the way. -- Mel Gorman SUSE Labs -- 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