Add experiment for background Perfetto init [chromium/src : main]

[Peter Birk Pakkenberg (Gerrit)]

Attention needed from Abhijith Nair

Peter Birk Pakkenberg added 1 comment

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File-level comment, Patchset 2 (Latest):

Peter Birk Pakkenberg . resolved

Hi Abhijith, could you give this a first review before I send it to others?

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[Abhijith Nair (Gerrit)]

Attention needed from Peter Birk Pakkenberg

Abhijith Nair added 2 comments

File android_webview/glue/java/src/com/android/webview/chromium/WebViewChromiumFactoryProvider.java

Line 615, Patchset 2 (Latest): TaskTraits.BEST_EFFORT,

Abhijith Nair . unresolved

This will end up blocking startup if it takes too long. Shouldn't this be higher priority?

File android_webview/java/src/org/chromium/android_webview/common/ProductionSupportedFlagList.java

Line 1087, Patchset 2 (Latest): + AwFeatures.WEBVIEW_EARLY_PERFETTO_INIT

Abhijith Nair . unresolved

Curious, does it make sense to consolidate all our perfetto flags into one flag and use feature params to select different behaviours? That way, I don't think we have to worry about a situation where multiple feature params are enabled at the same time?

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[Peter Birk Pakkenberg (Gerrit)]

Attention needed from Abhijith Nair

Peter Birk Pakkenberg added 2 comments

File android_webview/glue/java/src/com/android/webview/chromium/WebViewChromiumFactoryProvider.java

Line 615, Patchset 2: TaskTraits.BEST_EFFORT,

Abhijith Nair . resolved

This will end up blocking startup if it takes too long. Shouldn't this be higher priority?

Peter Birk Pakkenberg

Good point. Adjusted to USER_VISIBLE

File android_webview/java/src/org/chromium/android_webview/common/ProductionSupportedFlagList.java

Line 1087, Patchset 2: + AwFeatures.WEBVIEW_EARLY_PERFETTO_INIT

Abhijith Nair . resolved

Curious, does it make sense to consolidate all our perfetto flags into one flag and use feature params to select different behaviours? That way, I don't think we have to worry about a situation where multiple feature params are enabled at the same time?

Peter Birk Pakkenberg

Possibly, but it would still only have one variant tested at a time, and the flags UI does not support params afaik, so this approach allows the flag UI to select each arm.

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[Abhijith Nair (Gerrit)]

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Abhijith Nair voted Code-Review+1

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+1

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[Peter Birk Pakkenberg (Gerrit)]

Attention needed from Richard (Torne) Coles

Peter Birk Pakkenberg added 1 comment

Patchset-level comments

File-level comment, Patchset 4 (Latest):

Peter Birk Pakkenberg . resolved

Hi Torne, would you mind taking a look at this? It is more complex than the previous CL that added an experiment for background startup because it makes sure that Perfetto is in fact initialized before it proceeds with main thread startup.

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[Richard (Torne) Coles (Gerrit)]

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Richard (Torne) Coles added 1 comment

File android_webview/browser/aw_browser_process.cc

Line 402, Patchset 4 (Latest): if (g_initializing_perfetto_on_background_thread) {

Richard (Torne) Coles . unresolved

If the call to InitPerfetto has been posted to a background thread then I don't think anything guarantees that it will have reached the point of setting this variable to true before this function is called?

I think you would need to always signal the event and always wait on it, and only read `g_initializing_perfetto_on_background_thread` *after* successfully waiting for it if you want to know whether it was done on the background thread or not for the purposes of the metric.

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