forms.js and UserAgentOverrides.jsm overhead was significant on startup.

Comment on attachment 707338 [details] [diff] [review] Precompile forms.js and preload UserAgenOverrides.jsm Review of attachment 707338 [details] [diff] [review]: ----------------------------------------------------------------- ::: dom/ipc/preload.js @@ +71,5 @@ > Cc["@mozilla.org/thread-manager;1"].getService(Ci["nsIThreadManager"]); > Cc["@mozilla.org/toolkit/app-startup;1"].getService(Ci["nsIAppStartup"]); > Cc["@mozilla.org/uriloader;1"].getService(Ci["nsIURILoader"]); > > + Services.io.getProtocolHandler("app"); I'm not sure this is useful, since the AppsProtocolHandler constructor doesn't do much.

I added that so we execute AppProtocolHandler.js code, but I didn't test it in isolation so you're right that it may not be a win.

(In reply to Chris Jones [:cjones] [:warhammer] from comment #3) > I added that so we execute AppProtocolHandler.js code, but I didn't test it > in isolation so you're right that it may not be a win. It worth it imho. All the JS API / Modules instantiated on the main loading path seems to hurt. Also are you not going to call UserAgentOverrides.init(); twice? Once in the preload process and once in uao_child.js when it will be inserted via loadFrameScript?

(In reply to Chris Jones [:cjones] [:warhammer] from comment #3) > I added that so we execute AppProtocolHandler.js code, but I didn't test it > in isolation so you're right that it may not be a win. This gets 5-6 samples out of a profile in AppProtocolHandler.js:1. I think this is a valid win.

(In reply to Vivien Nicolas (:vingtetun) (:21) from comment #4) > Also are you not going to call UserAgentOverrides.init(); twice? Once in the > preload process and once in uao_child.js when it will be inserted via > loadFrameScript? The code has an "already-initialized" check. So we call it twice but only run it once.

Oh, I see what you mean. We only TryCacheAndCompile("UAO_child.js"), we don't run it. But since it doesn't depend on content, we could go ahead and run that and remove the explicit call to UAO.init().

Actually, with the way UAO_child.js is set up, we're technically breaking the rules here and always loading the overrides, regardless of product. The way it's set up right now we can't legally preload it :|.

Any suggestion for how we can do this without resorting to something "unclean" like a feature-pref for overrides?

For example, I might write code to check if there are any override prefs set and then load the UAO code if so, but that might horrify chrome hackers.

Feedback ping. This is a very nice measurable win.

I'm going to add a feature pref for UA overrides and check it in preload.js to see whether to load and init() UserAgentOverrides, and remove UAO_child.js entirely. Anyone object?

I would be very happy to see UAO_child.js disappear.

Comment on attachment 710432 [details] [diff] [review] Precompile forms.js and preload UserAgenOverrides.jsm, v2 Review of attachment 710432 [details] [diff] [review]: ----------------------------------------------------------------- ::: modules/libpref/src/init/all.js @@ +27,5 @@ > // This pref exists only for testing purposes. In order to disable all > // overrides by default, don't initialize UserAgentOverrides.jsm. > pref("general.useragent.site_specific_overrides", true); > > +// Enable UA overrides for shipping product code. I know what the pref does, but I fail to understand the English sentence. This may be just me, however ;)

Pushed with more verbose comment https://hg.mozilla.org/integration/mozilla-inbound/rev/2716ae058067

Comment on attachment 710432 [details] [diff] [review] Precompile forms.js and preload UserAgenOverrides.jsm, v2 Low-risk patch that significantly reduces time spent on critical startup path in app processes.

Comment on attachment 710432 [details] [diff] [review] Precompile forms.js and preload UserAgenOverrides.jsm, v2 Please go ahead with uplift to the tip of mozilla-b2g18 branch for v1.0.1

https://hg.mozilla.org/releases/mozilla-b2g18/rev/e4ffa0660d88 https://hg.mozilla.org/releases/mozilla-b2g18/rev/d3401943481d