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 <cores> -b <memory> > > Where <cores> is the number of cores to spawn threads on, and <memory> > is the amount of memory to reserve from each core. The <memory> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>