1853720 - Add a profiler label variant that does nothing if the profiler isn't running

Status: RESOLVED FIXED

(Core :: Gecko Profiler, enhancement)

Description

[Markus Stange [:mstange]]

On Speedometer3, even with the profiler disabled, 1.4% of the innerHTML setter is spent pushing and popping profiler labels for the frame constructor:

https://share.firefox.dev/48m13lm 42702 samples in innerHTML overall
https://share.firefox.dev/48dL34R 606 samples in AutoProfilerLabel code

These labels use the AUTO_PROFILER_LABEL macro. I think it would make sense to add an AUTO_PROFILER_LABEL_HOT macro which checks whether the profiler is running before it pushes the label.

Comment 1

[Markus Stange [:mstange]]

Attachment: Bug 1853720 - Inline-away AutoProfilerLabel::Push. r=aabh

Comment 2

[Markus Stange [:mstange]]

Attachment: Bug 1853720 - Add a "hot" variant of AUTO_PROFILER_LABEL, for lower overhead when the profiler is disabled. r=aabh

The overhead is showing up in Speedometer 3, especially in the innerHTML setter
when it calls into the frame constructor.

Full breakdown of callers across sp3 is here: https://share.firefox.dev/3rfckTG

Time spent in AutoProfilerLabel during TodoMVC-jQuery innerHTML:
Before: https://share.firefox.dev/3Znlydp 378 sampes
After: https://share.firefox.dev/45VdVgr 71 samples

Depends on D188486

Comment 3

[Markus Stange [:mstange]]

Attachment: Bug 1853720 - Add MOZ_UNLIKELY to the AutoProfilerLabel destructor. r=aabh

This probably doesn't tell the compiler anything it doesn't already know from PGO,
but it shouldn't hurt either.

Depends on D188487

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/08832aa3ba61
Inline-away AutoProfilerLabel::Push. r=aabh,profiler-reviewers
https://hg.mozilla.org/integration/autoland/rev/446af5901170
Add a "hot" variant of AUTO_PROFILER_LABEL, for lower overhead when the profiler is disabled. r=aabh,profiler-reviewers

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/08832aa3ba61
https://hg.mozilla.org/mozilla-central/rev/446af5901170