Re: About rtla osnoise and timerlat usage

Daniel Bristot de Oliveira
2023-02-22T18:06:42Z

On 2/22/23 09:39, Prasad Pandit wrote:
> Hello Daniel,
>
> Thank you so much for your reply, I appreciate it.
>
> On Wed, 22 Feb 2023 at 17:30, Daniel Bristot de Oliveira <bristot@kernel.org <mailto:bristot@kernel.org>> wrote:
>
> This is the timerlat's timer, so it is expected. What this trace is pointing is to
> a possible exit from idle latency... so idle tune is required for this system
> and *this metric*... but
>
>
> * Idle tune?

ops, I did not reply to this: idle tuning is configuring the system to avoid deep idle states.

An easy way to do it is either setting idle=poll or enabling the "--dma-latency 0" in timerlat.

But this is only a "problem" for timerlat/cyclictest, not for oslat/osnoise as they measure
the noise as they run - so they CPU does not go idle.

>
> Yes, that is expected on timerlat in an isolated CPU. But not with osnoise/oslat kind of tool,
> as they keep running, while timerlat/cyclictest go to sleep.
>
>
> * I see, okay.
>
> Let me know how rtla osnoise results are, so I can help more.
>
>
> * Yes, I've been running oslat(1) and rtla-osnoise(1) too.
>    Please see:
>     oslat(1) log -> https://0bin.net/paste/T0PDXHz5#AnNEzkTRxQVT1gvAqKM43jW+yhqilbNbFqHIHHpy4MY <https://0bin.net/paste/T0PDXHz5#AnNEzkTRxQVT1gvAqKM43jW+yhqilbNbFqHIHHpy4MY>
>     rtla-osnoise-top(1) log -> https://0bin.net/paste/8qwjebnZ#22sfTYTv68JAAMHZJhnCBTP-uvP7Mxj8ipAVbuQVsiy <https://0bin.net/paste/8qwjebnZ#22sfTYTv68JAAMHZJhnCBTP-uvP7Mxj8ipAVbuQVsiy>
>
> Thank you.
> ---
>   - P J P