On Thu, Mar 21, 2019 at 10:25 AM Denys Vlasenko <dvlas...@redhat.com> wrote:
>
> >
> > But iirc pushf/popf isn't really that expensive - in fact I think it's
> > pretty cheap when system flags don't change.
>
> I did not see evidence of this. In my testing,
> POPF is always ~20 cycles, even if popped flags are identical to current
> state of flags.
It may have been an artifact on just some older CPU's. I have this
distinct memory of popf that changed IF being more expensive, but
maybe that was the Pentium 4 days.
Or maybe it's just that my memory is garbage.
Linus
