On Fri, 29 Apr 2011 14:38:08 +0900
Takuya Yoshikawa <takuya.yoshikawa@xxxxxxxxx> wrote:
> On Thu, 28 Apr 2011 19:46:00 -0700
> Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>
> > Avi Kivity <avi@xxxxxxxxxx> writes:
> > >
> > > Good optimization. copy_from_user() really isn't optimized for short
> > > buffers, I expect much of the improvement comes from that.
> >
> > Actually it is equivalent to get_user for the lenghts supported by
> > get_user, assuming you pass in a constant length. You probably do not.
> >
> > -Andi
>
>
> Weird, I actually measured some changes even after dropping other parts
> than get_user() usage.
>
> Only I can guess for that reason is the reduction of some function calls
> by inlining some functions.
A bit to clarify.
Original path:
kvm_read_guest_page_mmu()
kvm_read_guest_page()
copy_from_user()
Takuya
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