Re: [PATCH 2/2] app/testpmd: add testpmd based sleeping

Re: [PATCH 2/2] app/testpmd: add testpmd based sleeping

[Anthony Harivel]

Ferruh Yigit, Mar 16, 2023 at 18:05:
> Hi Anthony,
>
> What is the motivation here?

Hi Ferruh,

AFAIK testpmd is the reference tool used for CI and tests whether it is
for functional or performance tests and I think it would be in
everyone's interest to consume less CPU during them. Moreover, all
patches coming to the ML are going through validation tests and this
could reduce the maintenance cost of the project.

Re: [PATCH 2/2] app/testpmd: add testpmd based sleeping

[Stephen Hemminger]

On Fri, 17 Mar 2023 12:09:04 +0100
"Anthony Harivel" <aharivel@redhat.com> wrote:

> Ferruh Yigit, Mar 16, 2023 at 18:05:
> > Hi Anthony,
> >
> > What is the motivation here?  
> 
> Hi Ferruh,
> 
> AFAIK testpmd is the reference tool used for CI and tests whether it is
> for functional or performance tests and I think it would be in
> everyone's interest to consume less CPU during them. Moreover, all
> patches coming to the ML are going through validation tests and this
> could reduce the maintenance cost of the project.

But it introduces another variable, and the performance would vary based on
sleeping and HW interaction. I think testpmd should just run with 100% CPU,
and leave the heuristics stuff to some of the example applications.

Re: [PATCH 2/2] app/testpmd: add testpmd based sleeping

[Ferruh Yigit]

On 3/17/2023 11:09 AM, Anthony Harivel wrote:
> Ferruh Yigit, Mar 16, 2023 at 18:05:
>> Hi Anthony,
>>
>> What is the motivation here?
> 
> Hi Ferruh,
> 
> AFAIK testpmd is the reference tool used for CI and tests whether it is
> for functional or performance tests and I think it would be in
> everyone's interest to consume less CPU during them. Moreover, all
> patches coming to the ML are going through validation tests and this
> could reduce the maintenance cost of the project.
> 

I don't think testpmd CPU usage is a real concern, it is only used by
limited number of people and only for a limited duration.
And optimizations like this may jeopardize its main task.


On the other hand, CPU/power consumption of a DPDK application in
production is a concern, and there may be many parties interested in to
reduce watt/core with a reasonable performance impact.

There is already a 'power' library for this purpose, to enable power
optimizations for all DPDK applications, instead of just implementing
them on a specific application (like testpmd).

In my experience heuristics approaches (as done in your patch) depends
on workload, while it helps for some usecases it may hurt in others.
Still there may be customers willing to test a specific one for a
specific workload.

What do you think to have these heuristics approaches implemented in the
power library, and add a new power sample application that selects one
of existing algorithm as a kind of plugin?
It can start with single algorithm, that is what you used in this patch.
But overall how to add them into power library needs to be designed.

cc'ed @Dave as power library/sample maintainer.