Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33

Avi Kivity
2009-12-21T17:05:06Z

On 12/21/2009 06:56 PM, Gregory Haskins wrote:
>> I'm working on disappearing EOI exits on older hardware as well. Same
>> idea as the old TPR patching, without most of the magic.
>>
>>
> While I applaud any engineering effort that results in more optimal
> execution, if you are talking about what we have discussed in the past
> its not quite in the same league as my proposal.
>

I don't doubt this for a minute.

> You are talking about the ability to optimize the final EOI if there are
> no pending interrupts remaining, right? The problem with this approach
> is it addresses the wrong side of the curve: That is, it optimizes the
> code as its about to go io-idle. You still have to take an extra exit
> for each injection during the heat of battle, which is when you actually
> need it most.
>

No, it's completely orthogonal. An interrupt is injected, the handler
disables further interrupts and EOIs, then schedules the rest of the
handling code. So long as there as packets in the ring interrupts won't
be enabled and hence there won't be any reinjections.

Different interrupt sources still need different interrupts, but as all
of your tests have been single-interface, this can't be the reason for
your performance.

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