Messages in this thread | | | Date | Wed, 11 Jul 2012 19:31:47 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler |
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On 07/11/2012 07:29 PM, Raghavendra K T wrote: > On 07/11/2012 02:30 PM, Avi Kivity wrote: >> On 07/10/2012 12:47 AM, Andrew Theurer wrote: >>> >>> For the cpu threads in the host that are actually active (in this case >>> 1/2 of them), ~50% of their time is in kernel and ~43% in guest. This >>> is for a no-IO workload, so that's just incredible to see so much cpu >>> wasted. I feel that 2 important areas to tackle are a more scalable >>> yield_to() and reducing the number of pause exits itself (hopefully by >>> just tuning ple_window for the latter). >> >> One thing we can do is autotune ple_window. If a ple exit fails to wake >> anybody (because all vcpus are either running, sleeping, or in ple >> exits) then we deduce we are not overcommitted and we can increase the >> ple window. There's the question of how to decrease it again though. >> > > I see some problem here, If I interpret situation correctly. What > happens if we have two guests with one VM having no over-commit and > other with high over-commit. (except when we have gang scheduling). > Sorry, I meant less load and high load inside the guest.
> Rather we should have something tied to VM rather than rigid PLE > window.
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