On Fri, Aug 31, 2018 at 04:53:50AM -0700, Srikar Dronamraju wrote: > * Peter Zijlstra <pet...@infradead.org> [2018-08-31 13:26:39]: > > > On Fri, Aug 31, 2018 at 01:12:53PM +0200, Peter Zijlstra wrote: > > > NAK, not until you've fixed every cpu_to_node() user in the kernel to > > > deal with that mask changing. > > > > Also, what happens if userspace reads that information; uses libnuma and > > then you go and shift the world underneath their feet? > > > > > This is absolutely insane. > > > > The topology events are suppose to be very rare. > From whatever small experiments I have done till now, unless tasks are > bound to both cpu and memory, they seem to be coping well with topology > updates. I know things weren't optimal after a topology change but they > worked. Now after 051f3ca02e46 "Introduce NUMA identity node sched > domain", systems stall. I am only exploring at ways to keep them working > as much as they were before that commit.
I'm saying things were fundamentally buggered and this just made it show. If you cannot guarantee cpu:node relations, you do not have NUMA, end of story.