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

From: Dietmar Eggemann
Date: Tue May 30 2023 - 06:03:42 EST

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.