Re: [PATCH v2 05/17] trace: energy_model: Add trace event for EM runtime modifications

[Lukasz Luba]

On 5/30/23 11:03, Dietmar Eggemann wrote:
> On 12/05/2023 11:57, Lukasz Luba wrote:
> > The Energy Model (EM) supports runtime modifications. Track the changes
> > in order to do post-processing analysis. Don't use arrays in the trace
> > event, since they are not properly supported by the tools. Instead use
> > simple "unroll" with emitting the trace event for each EM array entry
> > with proper ID information. The older debugging mechanism which was
> > the simple debugfs which dumping the EM content won't be sufficient for
> > the modifiable EM purpose. This trace event mechanism would address the
> > needs.
>
> Do we really need a full trace_event for this? Can we not follow the
> task scheduler rule which says no new trace_events and use a trace_point
> here? The footprint in the kernel would be so much smaller.
>
> E.g. pelt_cfs_tp
>
> 0 sched.h  694 DECLARE_TRACE(pelt_cfs_tp,
> 1 core.c   106 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
> 2 fair.c  3937 trace_pelt_cfs_tp(cfs_rq);
>
> And then this patch should be after the section with the functional changes.
>
> [...]

I agree. I will change that approach and create tracepoint. Also, I'll
move it to the patch at the end of the functional changes.