[PATCH] benchtests: Restore the clock_gettime option

[H.J. Lu]

On Tue, May 19, 2020 at 2:18 PM Alexander Monakov <amonakov@ispras.ru> wrote:
>
>
>
> On Tue, 19 May 2020, H.J. Lu via Libc-alpha wrote:
>
> > commit 7621e38bf3c58b2d0359545f1f2898017fd89d05
> > Author: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
> > Date:   Tue Jan 29 17:43:45 2019 +0000
> >
> >     Add generic hp-timing support
> >
> > removed the clock_gettime option.  On x86, fewer cycles doesn't
> > necessarily mean faster exection due to frequency drop.  We should
> > restore the clock_gettime option.
>
> Can you please elaborate more which x86 CPUs you have in mind here,
> as since Nehalem (2008) when invariant TSC was introduced, the rdtsc(p)
> instructions count at a fixed rate rather than at CPU clock rate.
> And before 2008, there were no turbo frequencies and no AVX frequency drop.

https://stackoverflow.com/questions/56852812/simd-instructions-lowering-cpu-frequency

-- 
H.J.