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@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>