Re: [PATCH v4 4/6] perf arm-spe: Assign kernel time to synthesized event

[Leo Yan]

On Fri, Apr 16, 2021 at 03:51:25PM +0300, James Clark wrote:

[...]

> >> I noticed that in arm_spe_recording_options() the TIME sample bit is set regardless of any options.
> >> I don't know of a way to remove this, and if there isn't, does that mean that all the code in this
> >> file that looks at spe->timeless_decoding is untested and has never been hit?
> >>
> >> Unless there is a way to get a perf file with only the AUXTRACE event and no others? I think that one
> >> might have no timestamp set. Otherwise other events will always have timestamps so spe->timeless_decoding
> >> is always false.
> > 
> > Good point.  To be honest, I never noticed this issue until you
> > mentioned this.
> > 
> > We should fix for the "timeless" flow; and it's questionable for the
> > function arm_spe_recording_options(), except for setting
> > PERF_SAMPLE_TIME, it also hard codes for setting
> > PERF_SAMPLE_CPU and PERF_SAMPLE_TID.  Might need to carefully go
> > through this function.
> > 
> 
> Yeah, it's not strictly related to your change, which is definitely an improvement.
> But maybe we should have a look at the SPE implementation relating to timestamps as a whole.

Totally agree, at least this patch series should not introduce any
barrier for timeless case.  I will go back to verify it; if you'd
like to fix timeless issue, please feel free to go ahead.

Thanks,
Leo