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. - Steve
