Boris Zbarsky [:bzbarsky] Assignee
	Description • 14 years ago

We throttle the refresh driver; we should throttle DOM timers too.  The issue is web compat...

On the other hand, I hear tell that other browsers are considering doing this, so at least we're not alone.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 1 • 14 years ago

Oh, for refresh driver we throttle to 1Hz, but once 2.0 ships I'll land a patch to throttle to an doubling-each-time interval.

I don't think we want the doubling behavior for DOM timers, though.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 2 • 14 years ago

nsGlobalWindow has its own concept of "active" which seems to do with focus.  I don't think we want to use that here, fwiw.

	Andreas Gal :gal
	Comment 4 • 14 years ago

Chrome is going to set the minimum interval to 0.5Hz I believe.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 5 • 14 years ago

Yeah, that's what the attached patch uses as the default pref value.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 6 • 14 years ago

Or rather it does 0.5s, which is what I think you meant.  We should clearly make it 1Hz to avoid that problem....

	Nickolay_Ponomarev
	Comment 7 • 14 years ago

Chromium issue is http://code.google.com/p/chromium/issues/detail?id=66078 and they seem to use 1s.

dev-doc-needed: https://developer.mozilla.org/en/DOM/window.setTimeout#Minimum_delay_and_timeout_nesting will need to mention this change if it lands.

	Johnny Stenback (:jst)
	Comment 8 • 13 years ago

Comment on attachment 511636 [details] [diff] [review]
Pretty easy to do if we want to!

Let's give this a shot! Patch looks good (and I'm fine with either 1 or 2Hz here, maybe go with 1 to match chrome?).

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 10 • 13 years ago

Pushed http://hg.mozilla.org/mozilla-central/rev/e328ab1bcb03 except I forgot to fix the commit message... I used a 1000ms clamp, but the commit message still says 500ms.  The correct number is 1000.

	Doug Turner (:dougt)
	Comment 11 • 13 years ago

is there anything here that mobile/e10s needs to do to get this benefit?

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 12 • 13 years ago

I don't think so.  You're already flagging docshells as inactive so images get discarded, right?

I can write up a testcase for you to test whether this patch is working if you want (pretty easy to do a manual test; hard to do an automated one).

	Doug Turner (:dougt)
	Comment 13 • 13 years ago

yes, i think we do.  alon would know specifically.  happy to run a test case.

	Alon Zakai (:azakai)
	Comment 14 • 13 years ago

I tested to make sure, and this works perfectly on mobile. Great stuff!

On a related note, this might make bug 588975 (stop animating images in background tabs) easier to do, which is also about reducing activity in inactive tabs.

	emmbugzilla
	Comment 16 • 13 years ago

This works on background tabs, but not on active tabs on minimized windows. Is this the expected behavior?

For comparison, in Chrome, the active tab of a minimized window is considered inactive.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 17 • 13 years ago

> Is this the expected behavior?

For now, yes.  Which tabs are active is under control of the user interface; it might be worth a bug on Firefox to mark the active tab in a minimized window as inactive.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 18 • 13 years ago

I filed bug 648045 and bug 648046 on applying the throttling in more cases.

	Eric Shepherd [:sheppy]
	Comment 19 • 13 years ago

Documentation updated:

https://developer.mozilla.org/en/DOM/window.setTimeout#Inactive_tabs

Also updated Firefox 5 for developers.

	Grant Galitz
	Comment 20 • 13 years ago

Is there a specific DOM event that gets fired when the clamping to 1000 milliseconds starts (We would need to register a listener for it first of course though for it to be exposed...)? This currently trashes the JS GameBoy Color emulator audio when it's running inside of an inactive tab, as everything is driven in it at 16 ms intervals by a sole setInterval.

So the question remains, is there a unique DOM event that would fire solely for this throttling, to warn the web app of the slowdown? Doing normal timestamp comparisons is not the best, due to slow browsers (mobile especially) and timestamp checking for automatic pausing could get hacky.

	Boris Zbarsky [:bzbarsky] Assignee
	Comment 21 • 13 years ago

> Is there a specific DOM event that gets fired

At this point, yes: http://www.w3.org/TR/2011/WD-page-visibility-20110602/#sec-visibilitychange-event

	Grant Galitz
	Comment 22 • 13 years ago

Thanks