1141283 - Compensate for stackwalk duration and sleep overhead when determining sampler sleep time

Status: RESOLVED FIXED

(Core :: Gecko Profiler, defect)

Description

[Markus Stange [:mstange]]

Attachment: patch

I didn't touch the Windows implementation because apparently we're not using SleepMicro there yet.

Comment 1

[Benoit Girard (:BenWa)]

Have you looked into the worse case scenarios when the sampling rate is faster than the sample duration?

Comment 2

[Markus Stange [:mstange]]

Good point, no I haven't.

Comment 3

[Markus Stange [:mstange]]

I've tried this locally on Mac now, by setting the sample interval to 0.0002 and profiling main thread + compositor thread. This resulted in a "real interval" of 0.02ms, so I suppose the profiling overhead of stackwalking+js on Mac is about 0.01ms per thread on this machine. With that profiling interval, the browser is very slow but still usable; simple pages scroll at 30fps, a complex cleopatra tree scrolls at 1fps.

Comment 4

[Markus Stange [:mstange]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/1ec1ec82f440

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/1ec1ec82f440