Re: [PATCH 0/18][RFC] Nested Paging support for Nested SVM (aka NPT-Virtualization)

From: Alexander Graf
Date: Wed Mar 03 2010 - 18:45:14 EST

On 03.03.2010, at 20:12, Joerg Roedel wrote:

> Hi,
> here are the patches that implement nested paging support for nested
> svm. They are somewhat intrusive to the soft-mmu so I post them as RFC
> in the first round to get feedback about the general direction of the
> changes. Nevertheless I am proud to report that with these patches the
> famous kernel-compile benchmark runs only 4% slower in the l2 guest as
> in the l1 guest when l2 is single-processor. With SMP guests the
> situation is very different. The more vcpus the guest has the more is
> the performance drop from l1 to l2.
> Anyway, this post is to get feedback about the overall concept of these
> patches. Please review and give feedback :-)

Nice job! It's great to see you finally got around to it :-).

Have you tracked what slows down SMP l2 guests yet? So far I've been assuming that IPIs just completely kill the performance, but I guess it shouldn't be that bad, especially now where you have sped up the #VMEXIT path that much.

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