* Dave Hansen <[email protected]> wrote:
> On 05/05/2015 10:58 AM, Ingo Molnar wrote:
> > x86/fpu: Cost of: XSAVE insn : 104 cycles
> > x86/fpu: Cost of: XRSTOR insn : 80 cycles
>
> Isn't there going to be pretty huge variability here depending on
> how much state you are xsave/xrstor'ing and if the init/modified
> optimizations are in play?
Hopefully there's such variability! :)
I thought to add measurements for that as well:
- to see the costs of this instruction family when various xstate
components are in 'init state' or not
- maybe even measure whether it can optimize based on whether things
got changed since the last save (which the SDM kind of alludes to
but which I doubt the hw does)?
This initial version only measures trivial init state save/restore
cost.
Thanks,
Ingo
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