From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 2AA836B01FD for ; Wed, 28 Apr 2010 23:57:30 -0400 (EDT) Date: Wed, 28 Apr 2010 22:57:18 -0500 From: Robin Holt Subject: Re: [PATCH v2] - Randomize node rotor used in cpuset_mem_spread_node() Message-ID: <20100429035718.GT4920@sgi.com> References: <20100428131158.GA2648@sgi.com> <20100428150432.GA3137@sgi.com> <20100428154034.fb823484.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100428154034.fb823484.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Jack Steiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, Apr 28, 2010 at 03:40:34PM -0700, Andrew Morton wrote: > On Wed, 28 Apr 2010 10:04:32 -0500 > Jack Steiner wrote: > > > Some workloads that create a large number of small files tend to assign > > too many pages to node 0 (multi-node systems). Part of the reason is that > > the rotor (in cpuset_mem_spread_node()) used to assign nodes starts > > at node 0 for newly created tasks. > > And, presumably, your secret testcase forks lots of subprocesses which > do the file creation? I think the test case he was using was aim7 or a kernel compile. Anything that opens a lot of small files will quickly deplete node 0. > > This patch changes the rotor to be initialized to a random node number > > of the cpuset. > > Why random as opposed to, say, inherit-rotor-from-parent? If I have something like a find ... -exec grep ..., won't the pages be biased towards the nodes adjacent to the parent's rotor values. Maybe I misunderstood Jack's problem, but I believe that was what he was seeing and why he chose random. I hope I did not misunderstand Jack's problem and mislead this discussion. Thanks, Robin Holt -- 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