[PATCH 0/4] coresight: Add ETR-PERF polling.

[James Clark]

On 21/04/2021 15:04, Daniel Kiss wrote:
> This series adds a feature to ETR-PERF that sync the ETR buffer to perf
> periodically. This is really handy when the system wide trace is used
> because in this case the perf won't sync during the trace. In a per-thread
> setup the traced program might not go to the kernel frequvently enought
> to collect trace. Polling helps in both usecases. Can be used with strobing.
> Tuning polling period is challanging, I'm working on an additional patch
> that adds some metrics to help tune the polling period.

Hi Daniel,

Is the expectation that leaving the polling period at 0 should have no affect
on the amount of data collected vs not using this patch?

I've been running the octane 2 benchmark on Chrome on Juno and get these results:

  No patch:             I consistently get 130MB of trace across dozens of runs.
  Patch, polling = 0:   Run 1 - 6.1MB
                        Run 2 - 4.7MB
  Patch, polling = 100: 1600MB


Thanks
James

> 
> Daniel Kiss (4):
>   coresight: tmc-etr: Advance buffer pointer in sync buffer.
>   coresight: tmc-etr: Track perf handler.
>   coresight: etm-perf: Export etm_event_cpu_path.
>   coresight: Add ETR-PERF polling.
> 
>  .../testing/sysfs-bus-coresight-devices-tmc   |   8 +
>  drivers/hwtracing/coresight/Makefile          |   2 +-
>  .../hwtracing/coresight/coresight-etm-perf.c  |  10 +-
>  .../hwtracing/coresight/coresight-etm-perf.h  |   1 +
>  .../coresight/coresight-etr-perf-polling.c    | 316 ++++++++++++++++++
>  .../coresight/coresight-etr-perf-polling.h    |  42 +++
>  .../hwtracing/coresight/coresight-tmc-core.c  |   2 +
>  .../hwtracing/coresight/coresight-tmc-etr.c   |  22 +-
>  drivers/hwtracing/coresight/coresight-tmc.h   |   2 +
>  9 files changed, 401 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/hwtracing/coresight/coresight-etr-perf-polling.c
>  create mode 100644 drivers/hwtracing/coresight/coresight-etr-perf-polling.h
>