Messages in this thread | | | From | Ingo Molnar <> | Date | Wed, 6 May 2015 06:11:04 +0200 | Subject | Re: [PATCH 207/208] x86/fpu: Add FPU performance measurement subsystem |
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* Dave Hansen <dave.hansen@linux.intel.com> 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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