[ovs-dev] [PATCH] dpif-netdev-perf: Clarify frequency number.

Stokes, Ian ian.stokes at intel.com
Wed Oct 10 15:43:05 UTC 2018

> On Tue, Sep 25, 2018 at 07:00:40PM +0300, Ilya Maximets wrote:
> > 'dpif-netdev/pmd-perf-show' command prints the frequency number
> > calculated from the total number of cycles spent for iterations for
> > the measured period. This number could be confusing, because users may
> > think that it should be equal to CPU frequency, especially on non-x86
> > systems where TSC frequency likely does not match with CPU one.
> >
> > Moreover, counted TSC cycles could differ from the HW TSC cycles in
> > case of a large number of PMD reloads, because cycles spent outside of
> > the main polling loop are not taken into account anywhere.
> > In this case the frequency will not match even TSC frequency.
> >
> > Let's clarify the meaning in order to avoid this misunderstanding.
> > 'Cycles' replaced with 'Used TSC cycles', which describes how many TSC
> > cycles consumed by the main polling loop. % of the total TSC cycles
> > now printed instead of GHz frequency, because GHz is unclear for
> > understanding, especially without knowing the exact TSC frequency.
> >
> > Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
> > ---
> Acked-by: Flavio Leitner <fbl at sysclose.org>

Thanks Ilya, looks good from my side also. I'll apply this as part of this week's pull request.


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