From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755895Ab3KGVw1 (ORCPT ); Thu, 7 Nov 2013 16:52:27 -0500 Received: from relay1.sgi.com ([192.48.179.29]:51823 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752205Ab3KGVwV (ORCPT ); Thu, 7 Nov 2013 16:52:21 -0500 Date: Thu, 7 Nov 2013 15:52:28 -0600 From: Alex Thorlton To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Subject: Re: BUG: mm, numa: test segfaults, only when NUMA balancing is on Message-ID: <20131107215228.GA4236@sgi.com> References: <20131016155429.GP25735@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131016155429.GP25735@sgi.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 16, 2013 at 10:54:29AM -0500, Alex Thorlton wrote: > Hi guys, > > I ran into a bug a week or so ago, that I believe has something to do > with NUMA balancing, but I'm having a tough time tracking down exactly > what is causing it. When running with the following configuration > options set: > > CONFIG_ARCH_SUPPORTS_NUMA_BALANCING=y > CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y > CONFIG_NUMA_BALANCING=y > # CONFIG_HUGETLBFS is not set > # CONFIG_HUGETLB_PAGE is not set > > I get intermittent segfaults when running the memscale test that we've > been using to test some of the THP changes. Here's a link to the test: > > ftp://shell.sgi.com/collect/memscale/ For anyone who's interested, this test has been moved to: http://oss.sgi.com/projects/memtests/thp_memscale.tar.gz It should remain there permanently. > > I typically run the test with a line similar to this: > > ./thp_memscale -C 0 -m 0 -c -b > > Where is the number of cores to spawn threads on, and > is the amount of memory to reserve from each core. The field > can accept values like 512m or 1g, etc. I typically run 256 cores and > 512m, though I think the problem should be reproducable on anything with > 128+ cores. > > The test never seems to have any problems when running with hugetlbfs > on and NUMA balancing off, but it segfaults every once in a while with > the config options above. It seems to occur more frequently, the more > cores you run on. It segfaults on about 50% of the runs at 256 cores, > and on almost every run at 512 cores. The fewest number of cores I've > seen a segfault on has been 128, though it seems to be rare on this many > cores. > > At this point, I'm not familiar enough with NUMA balancing code to know > what could be causing this, and we don't typically run with NUMA > balancing on, so I don't see this in my everyday testing, but I felt > that it was definitely worth bringing up. > > If anybody has any ideas of where I could poke around to find a > solution, please let me know. > > - Alex