Messages in this thread | | | Date | Wed, 11 Jul 2012 19:29:42 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler |
| |
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).
Rather we should have something tied to VM rather than rigid PLE window.
| |