Messages in this thread | | | Date | Wed, 11 Jul 2012 14:23:09 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler |
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On 07/11/2012 02:16 PM, Alexander Graf wrote: >> >>> yes the data structure itself seems based on the algorithm >>> and not on arch specific things. That should work. If we move that to common >>> code then s390 will use that scheme automatically for the cases were we call >>> kvm_vcpu_on_spin(). All others archs as well. >> >> ARM doesn't have an instruction for cpu_relax(), so it can't intercept >> it. Given ppc's dislike of overcommit, > > What dislike of overcommit?
I understood ppc virtualization is more of the partitioning sort. Perhaps I misunderstood it. But the reliance on device assignment, the restrictions on scheduling, etc. all point to it.
> >> and the way it implements cpu_relax() by adjusting hw thread priority, > > Yeah, I don't think we can intercept relaxing.
... and the lack of ability to intercept cpu_relax() ...
> It's basically a nop-like instruction that gives hardware hints on its current priorities.
That's what x88 PAUSE does. But we can intercept it (and not just any execution - we can restrict intercept to tight loops executed more than a specific number of times).
> That said, we can always add PV code.
Sure, but that's defeated by advancements like self-tuning PLE exits. It's hard to get this right.
-- error compiling committee.c: too many arguments to function
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