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

Flavio Leitner fbl at sysclose.org
Thu Sep 27 17:40:09 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>
> ---

LGTM
Acked-by: Flavio Leitner <fbl at sysclose.org>




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