On 31/01/2024 16:53, Ian Rogers wrote:

On Mon, Jan 29, 2024 at 4:49 AM Adrian Hunter adrian.hunter@intel.com wrote:

...

On 11/01/24 10:19, Adrian Hunter wrote:

...

Hi

Hardware traces, such as instruction traces, can produce a vast amount of trace data, so being able to reduce tracing to more specific circumstances can be useful.

The ability to pause or resume tracing when another event happens, can do that.

These patches add such a facilty and show how it would work for Intel Processor Trace.

Maintainers of other AUX area tracing implementations are requested to consider if this is something they might employ and then whether or not the ABI would work for them.

Changes to perf tools are now (since V4) fleshed out.

Changes in V4:

perf/core: Add aux_pause, aux_resume, aux_start_paused
  Rename aux_output_cfg -> aux_action
  Reorder aux_action bits from:
          aux_pause, aux_resume, aux_start_paused
  to:
          aux_start_paused, aux_pause, aux_resume
  Fix aux_action bits __u64 -> __u32

coresight: Have a stab at support for pause / resume
  Dropped

perf tools
  All new patches

Changes in RFC V3:

coresight: Have a stab at support for pause / resume
  'mode' -> 'flags' so it at least compiles

Changes in RFC V2:

  Use ->stop() / ->start() instead of ->pause_resume()
  Move aux_start_paused bit into aux_output_cfg
  Tighten up when Intel PT pause / resume is allowed
  Add an example of how it might work for CoreSight

Any more comments?

I think the tools side looks good. The parsing changes match the existing style. I wonder if it wouldn't be better to handle the valid strings (pause, resume, etc.) in the lexer rather than a separate parse function, but the pattern used matches the existing one. You can have my Acked-by on the tools changes, although the subtleties of ARM PMUs makes me somewhat nervous in this regard.

Thanks, Ian

Acked-by: James Clark james.clark@arm.com

I will get round to adding the Coresight support at some point. I checked the new parsing in this version and it seems to work ok.