Re: About rtla osnoise and timerlat usage

[Daniel Bristot de Oliveira <bristot@kernel.org>]

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