Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler

[Benjamin Herrenschmidt]

> ARM doesn't have an instruction for cpu_relax(), so it can't intercept
> it.  Given ppc's dislike of overcommit, and the way it implements
> cpu_relax() by adjusting hw thread priority, I'm guessing it doesn't
> intercept those either, but I'm copying the ppc people in case I'm
> wrong.  So it's s390 and x86.

No but our spinlocks call __spin_yield()  (or __rw_yield) which does
some paravirt tricks already.

We check if the holder is currently running, and if not, we call the
H_CONFER hypercall which can be used to "give" our time slice to the
holder.

Our implementation of H_CONFER in KVM is currently a nop though.

Cheers,
Ben.


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