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

[Rik van Riel]

On 07/09/2012 02:20 AM, Raghavendra K T wrote:
> Currently Pause Looop Exit (PLE) handler is doing directed yield to a
> random VCPU on PL exit. Though we already have filtering while choosing
> the candidate to yield_to, we can do better.
>
> Problem is, for large vcpu guests, we have more probability of yielding
> to a bad vcpu. We are not able to prevent directed yield to same guy who
> has done PL exit recently, who perhaps spins again and wastes CPU.
>
> Fix that by keeping track of who has done PL exit. So The Algorithm in series
> give chance to a VCPU which has:
>
>   (a) Not done PLE exit at all (probably he is preempted lock-holder)
>
>   (b) VCPU skipped in last iteration because it did PL exit, and probably
>   has become eligible now (next eligible lock holder)
>
> Future enhancemnets:

Your patch series looks good to me. Simple changes with a
significant result.

However, the simple heuristic could use some comments :)

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