1073545 - Add Vsync Markers to SPS Profiler

Status: RESOLVED FIXED

(Core :: Gecko Profiler, defect)

Description

[Mason Chang [Inactive] [:mchang]]

Instrument the SPS profiler to use vsync marker data. This will enable us to see when we miss a frame.

Comment 1

[Mason Chang [Inactive] [:mchang]]

Attachment: Output Vsync Timestamps in Profiles

The overall goal of this bug is to instrument the profiler to output HardwareComposer vsync times and display those in cleopatra. This portion enables the gecko profiler to create ProfilerMarkerPayloads at vsync intervals on the Compositor thread so we only have to profiler the compositor thread to get vsync markers.

Comment 2

[Mason Chang [Inactive] [:mchang]]

Attachment: Sample Profile w/ Vsync Timestamps

Comment 3

[Mason Chang [Inactive] [:mchang]]

Attachment: Screenshot of Vsync Markers in Cleopatra

Comment 4

[Mason Chang [Inactive] [:mchang]]

Attachment: Pull Request - Enable Cleopatra to display vsync markers

Comment 5

[Mason Chang [Inactive] [:mchang]]

From comment 1, the part I really dislike is how to synchronize between the android timestamp and mozilla timestamp. If a vsync interval is 16.6ms, and the HwcComposer::Vsync executes within roughly the same interval, we create a marker as the current timestamp. Then we dispatch vsyncs in TimeDuration::FromMicroseconds(androidTimestamp) distances from the start point. Otherwise, if we take TimeStamp::Now() in HwcComposer::Vsync, we will get timestamps of when the function executes, not when the vsync actually occurred. On a flame, using mozilla::TimeStamp now drifts between 14ms - 18ms which is not very good. If you have a better idea of how to sync mozilla::TimeStamps and Android TimeStamps, that'd be great!

Comment 6

[Mason Chang [Inactive] [:mchang]]

Attachment: Output Vsync Timestamps in Profiles

Found a better way. During HwcComposer::Init, we take timestamps in both android and mozilla timestamp objects. We use this as a reference point to create a Mozilla::TimeStamp object that is aligned with android timestamps.

Comment 7

[Benoit Girard (:BenWa)]

I also reviewed the github changes. Looks really nice. Great work!

Comment 8

[Mason Chang [Inactive] [:mchang]]

Attachment: Output Vsync Timestamps in Profiles. r=benwa

Carrying r+. Fixed a whitespace and updated patch to proper title. Try: https://tbpl.mozilla.org/?tree=Try&rev=caddcd330ce8.

Also updated MDN to document how to read the profiler frames data.

Comment 9

[Mason Chang [Inactive] [:mchang]]

Comment on attachment 8497192 [details] [review]
Pull Request - Enable Cleopatra to display vsync markers

Updated github pull request with comments from the pull request. I also made the vsync marker 0.5 so it makes it harder to tell it is a bar. Also have a wiki from comment 8.

Comment 10

[Mason Chang [Inactive] [:mchang]]

Comment on attachment 8497192 [details] [review]
Pull Request - Enable Cleopatra to display vsync markers

Landed on Cleopatra Front End

Comment 11

[Mason Chang [Inactive] [:mchang]]

Try issues on OS x 10.8. Trying again - https://tbpl.mozilla.org/?tree=Try&rev=36795dc453ba

Comment 12

[Mason Chang [Inactive] [:mchang]]

Attachment: Bug 1073545 - Add Vsync Timestamps to Profiler. r=benwa

Carrying r+. Modified to fix a build issue on b2g emulators. Successful try - https://tbpl.mozilla.org/?tree=Try&rev=7e403d341172

Comment 13

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/094128a6d5a6

Comment 14

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/094128a6d5a6