Messages in this thread | | | Date | Tue, 15 Aug 2017 15:07:14 +0200 | From | Frederic Weisbecker <> | Subject | Re: [RFC PATCH 7/9] housekeeping: Use own boot option, independant from nohz |
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On Mon, Aug 14, 2017 at 08:29:46PM +0200, Mike Galbraith wrote: > On Mon, 2017-08-14 at 13:34 -0400, Luiz Capitulino wrote: > > On Mon, 14 Aug 2017 19:01:09 +0200 > > > > > What is the source of the load balancing inducing such latency when a single > > > task is affine to a CPU? If this is idle load balancing, it is now affine to > > > housekeepers. If this is task wakeup then it's suprising because select_task_rq() > > > is optimized toward single CPU affinity. > > > > I guess it was idle load balancing, but I don't remember because this > > was a few years ago. I think this might be reproducible without using > > isolcpus=. I'll give it a try shortly and let you know. > > idle_balance() can swamp other noise by a couple orders of magnitude,
Ah I missed that one. Is there any way we can also lower the overhead there? It looks unfortunately hard to tell if there is only one task affine to a given CPU, assertion on top of which we could make a fast exit.
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