linux-kernel - Re: [PATCH 8/13] KVM: vcpu execution loop

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Message-ID: <453D2FFA.3040506@qumranet.com>
Date:	Mon, 23 Oct 2006 23:11:22 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	Antonio Vargas <windenntw@...il.com>
CC:	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/13] KVM: vcpu execution loop

Antonio Vargas wrote:
>>
>> I could do that, but I feel that's more brittle.  I might need more (or
>> other) fields later on.  It will also cost me more  pushes on the stack
>> (no real performance or space impact, just C64-era frugality).
>
> maybe thats the mindsent needed to make these virtual cpu patches
> without eating away all the cpu power with more than needed
> abstractions ;)
>

Unfortunately not.  Saving a cycle or two doesn't help when a vm exit 
costs thousands of cycles, and worse, kills your tlb.

The key is eliminating unnecessary exits.  I have plans for massively 
optimizing the mmu virtualization, and the next AMD core will do that in 
hardware (look for a "nested page tables" sticker before you buy).

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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