Re: rt-tests: cyclictest: Add option to specify main pid affinity

["Ahmed S. Darwish" <a.darwish@linutronix.de>]

Hi Jonathan,

On Mar 21, 2021, Jonathan Schwender wrote:
>
> On 2/22/21 5:20 PM, Ahmed S. Darwish wrote:
> >
> > Do you also have any numbers showing different results
> > with/without "--mainaffinity"?
>
> Sorry for the delay. I do have some numbers now, and there is a
> benefit to using this option if CPU isolation + CAT are
> used. Otherwise it's not really visible.
>

Thanks a lot for the results.

Since I'm doing some CAT-related stuff on RT tasks vs. GPU workloads,
I'm curious, how much was the benefit of CAT ON/OFF?

In your benchmarks you show that the combination of --mainaffinity, CPU
isolation, and CAT, improves worst case latency by 2 micro seconds. If
you keep everything as-is, but disable only CAT, how much change happens
in the results?

Also, how many classes of service (CLOS) your CPU has? How was the cache
bitmask divided vis-a-vis the available CLOSes? And did you assign
isolated CPUs to one CLOS, and non-isolated CPUs to a different CLOS? Or
was the division more granular?

Kind regards,

--
Ahmed S. Darwish
Linutronix GmbH