Re: [PATCH 3/6] KVM MMU: optimize/cleanup for marking parent unsync

Marcelo Tosatti
2010-04-13T15:01:37Z

On Tue, Apr 13, 2010 at 09:53:07AM +0800, Xiao Guangrong wrote:
>
>
> Marcelo Tosatti wrote:
>
> > Xiao,
> >
> > Did you actually see this codepath as being performance sensitive?
>
> Actually, i not run benchmarks to contrast the performance before this patch
> and after this patch.
>
> >
> > I'd prefer to not touch it.
>
> This patch avoids walk all parents and i think this overload is really unnecessary.
> It has other tricks in this codepath but i not noticed? :-)

My point is that there is no point in optimizing something unless its
performance sensitive. And as i recall, mmu_unsync_walk was much more
sensitive performance wise than parent walking. Actually, gfn_to_memslot
seems more important since its also noticeable on EPT/NPT hosts.