Re: [PATCH v7 1/3] x86/fpu: Measure the Latency of XSAVE and XRSTOR

[Yi Sun]

On 21.09.2023 09:52, Andi Kleen wrote:
> > It seems unnecessarily complex: why does it have to measure latency
> > directly? Tracepoints *by default* come with event timestamps. A latency
> > measurement tool should be able to subtract two timestamps to extract the
> > latency between two tracepoints...
> >
> > In fact, function tracing is enabled on all major Linux distros:
> >
> >   kepler:~/tip> grep FUNCTION_TRACER /boot/config-6.2.0-33-generic
> >   CONFIG_HAVE_FUNCTION_TRACER=y
> >   CONFIG_FUNCTION_TRACER=y
> >
> > Why not just enable function tracing for the affected FPU context switching
> > functions?
>
> Or use PT address filters to get it even accurately, as described
> in [1]. In any case I agree the trace points are not needed.
Hi Andi,

Here, we have implemented latency measurement for all x86 platforms, not
just for Intel but also for other vendors like AMD. This allows us to 
obtain comparable data.

Thanks
   --Sun, Yi