On Mon, Oct 22, 2018 at 03:21:20PM -0400, Steven Sistare wrote: > On 10/22/2018 2:47 PM, Steven Sistare wrote: > > On 10/22/2018 1:06 PM, Peter Zijlstra wrote: > >> On Mon, Oct 22, 2018 at 07:59:40AM -0700, Steve Sistare wrote: > >>> The STEAL feature causes regressions on hackbench on larger NUMA systems, > >>> so disable it on systems with more than sched_steal_node_limit nodes > >>> (default 2). > >> > >> How come? From a quick read the stealing is per LLC, where do we steal > >> across nodes? > > > > See the complete explanation in this patch. It is deeper than can be > > gleaned > > from a quick read. > > I should have said a bit more. Your quick take on stealing is correct, we do > not steal across nodes. However, stealing reduces average run queue length > which > influences wake_affine migrations. Now see the complete explanation.
Right; read a bit more just now. hackbench is a fairly poor benchmark for numa performance. One that comes to mind is multi wharehouse specjbb stuff (assuming you have numa balance enabled of course).
