Re: [PATCH] KVM: x86: small optimization for is_mtrr_mask calculation

[Wanpeng Li]

On Fri, 6 Mar 2020 at 10:23, linmiaohe <linmiaohe@xxxxxxxxxx> wrote:
>
> hpa@xxxxxxxxx wrote:
> >>On March 5, 2020 6:05:40 PM PST, linmiaohe <linmiaohe@xxxxxxxxxx> wrote:
> >>Hi,
> >>Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> >>Many thanks for suggestion. What do you mean is like this ?
> >>
> >>      index = (msr - 0x200) >> 1;
> >>      is_mtrr_mask = msr & 1;
> >>
> >>Thanks again.
> >
> >You realize that the compiler will probably produce exactly the same code, right? As such, it is about making the code easy for the human reader.
> >
> >Even if it didn't, this code is as far from performance critical as one can possibly get.
>
> Yep, it looks gain little. Thanks.

Please post the performance number when you mention optimize XXX later.

    Wanpeng