Currently instantiating the nsThread and MessageLoop for the Android UI thread requires the main thread to block while they are created. It would be better to try and asynchronously create them and then only block if they are queried before they have been created on the Android UI thread.

Comment on attachment 8823884 [details] [diff] [review] 0001-Bug-1328747-Make-Android-UI-nsThread-and-MessageLoop-creation-asynchronous-r-17010416-05cd641.patch Review of attachment 8823884 [details] [diff] [review]: ----------------------------------------------------------------- That is some gnarly code.

Pushed by rbarker@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/7ba48de0e021 Make Android UI nsThread and MessageLoop creation asynchronous r=froydnj

I see a perf win on some autophone devices: == Change summary for alert #4774 (as of January 11 2017 17:42 UTC) == Improvements: 5% remote-twitter summary android-4-2-armv7-api15 opt 2722.36 -> 2587.08 3% remote-blank summary android-6-0-armv8-api15 opt 869.46 -> 843.8 For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=4774

Comment on attachment 8823884 [details] [diff] [review] 0001-Bug-1328747-Make-Android-UI-nsThread-and-MessageLoop-creation-asynchronous-r-17010416-05cd641.patch Review of attachment 8823884 [details] [diff] [review]: ----------------------------------------------------------------- ::: widget/android/AndroidUiThread.cpp @@ +217,5 @@ > + if (!sInitialized) { > + return nullptr; > + } > + > + if (!sThread) { Drive-by: this is potentially racy btw. you could be returning an uninitialized nsThread here. It's best to always take the lock or add memory barriers. https://en.wikipedia.org/wiki/Double-checked_locking

(In reply to Jim Chen [:jchen] [:darchons] from comment #6) > Comment on attachment 8823884 [details] [diff] [review] > 0001-Bug-1328747-Make-Android-UI-nsThread-and-MessageLoop-creation- > asynchronous-r-17010416-05cd641.patch > > Review of attachment 8823884 [details] [diff] [review]: > ----------------------------------------------------------------- > > ::: widget/android/AndroidUiThread.cpp > @@ +217,5 @@ > > + if (!sInitialized) { > > + return nullptr; > > + } > > + > > + if (!sThread) { > > Drive-by: this is potentially racy btw. you could be returning an > uninitialized nsThread here. It's best to always take the lock or add memory > barriers. > > https://en.wikipedia.org/wiki/Double-checked_locking Good catch, I think I can also fix it by not assigning to the static vars until they have been initialized: RefPtr<nsThread> thread = new nsThread; // Initialize sThread = thread; // notify all I'll create a quick patch and post.