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

James Clark
2021-04-27T16:26:47Z

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