On Fri, Jun 22, 2018 at 1:19 PM Rik van Riel <r...@surriel.com> wrote: > > On Fri, 2018-06-22 at 09:01 -0700, Andy Lutomirski wrote: > > Hmm, fair enough. I think a better heuristic would be if the > > estimated idle duration is more than, say, 10ms. I *think* the code > > has been cleaned up enough that this is easy now. (Using time > > instead > > of C6 will make it a lot less dependent on which idle driver is in > > use.) > > This particular bit of code is only in intel_idle > though, and not every cpuidle governor estimates > an idle duration, nor does it get passed up the > stack (presumably because it not always exists). > > I will just drop this patch for now, and see if > adding back in the patch that skips manipulation > of the mm_cpumask(&init_mm), since that might make > leave_mm() a little cheaper. > > We would still have excess manipulation of the > bitmask when re-entering the task from what should > have been lazy TLB mode, but total cache line > contention would likely still be down from where > it is before that patch. >
Agreed. I think the right solution if you want that last little bit of performance is to get rid of the code in intel_idle and to add it in the core idle code. We have fancy scheduler code to estimate the idle time, and we should use it here IMO.
