Made a test case: http://plexode.com/eval3/#s=aekVQXANLVQMbA2FKAR4BERw9T2ABVVBISE1GNUpVpAkKAVycAQFwD3aXAUoMDAEGExYBEwEgAT0DUE9GwgEbwQNVWFDCm09enJxURlUqT1VGU1dCTQmgoqSmqEYNARIR6goDDcNLS5IDEQNeAA==

var i = 0;
function toggleTitle() {
  document.title = i++ % 2 ? "one" : "two";
}
setInterval(toggleTitle, 1000)

Turns out Safari doesn't support changing the title at all. I assume they allow it to change from JS up until some point in the page load.

Hmmm...there's something more going on here in Safari. Google Hangouts is able to dynamically change the tab title.

I can't tell what Safari is doing. Sometimes my plexode link works and sometimes it doesn't. Sometimes Hangouts works and sometimes it doesn't. I made a modified version so I could background the tab first before tab title changed and it seems to also sometimes work.

http://plexode.com/eval3/#s=aekVQXANLVQMbA2FKAR4BERw9T2ABVVBISE1GNUpVpAkKAVycAQFwD3aXAUoMDAEGExYBEwEgAT0DUE9GwgEbwQNVWFDCm09enJxURlWmTkZQVlUJqpcfrK4B1VUqT1VGU1dCTQmgoqSmqEYNARIR+QqcXvYWfIRBQcAYNYZLJaSAYRAZeAA=

This test case shows kind of what they're doing. When a tab is background they have some sort of super-linear backoff on setting tab title. I think that's actually just them increasingly throttling the background tab. We should probably figure out what they're doing.

http://plexode.com/eval3/#s=aekVQXANLVQMbA2FKAR4BERw9T2ABVVBISE1GNUpVpAkKAVycAQFwD3aXAUoMDJtPXpycVEZVpk5GUFZVCaqXH6yuAb5VKk9VRlNXQk0JoKKkpqhGDQESEeIKnF7fFuIRChwDDQNQS0uSAxEDXgA=

Can't say I understand what the logic is, but it looks like they grow up until a max clamp of 1 minute in background tabs.

I'm looking at the code as best I can tell and I'm not seeing this logic: https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/page/DOMTimer.cpp. Interestingly it looks like the clamp setInterval on a per-timer basis and they clamp setTimeout completely differently based off nesting level.

http://plexode.com/eval3/#s=aekVQXANJVQMbAx1RU0YBSkUePQNNUEhIRlOdHx0QlkYfAw0DS5GTYUoBHgERHD1PYU1CVFU1Sk6YtSVCVUYPT1BYCQq4T2ABVaBITUbAVdbNAVy5AQFwD3a0mQwMz99hT0ZYwMLkxcfJy83o4A9uCQifoaMIBQPNABBi1To9XKdgaZhSdDYBhIMAIJdbtYKYBwBXi+dxGZzejK9X8WckUjjPL0IJ5UI0iYRQKxVBLbDwfbkflZVFRPY5TK5CJoJaahazYawNAISCNKBS5L1HpNLDisAZQJZLSQDCIDLwAA==

That page had this output:

1: 2004
2: 1405
3: 2000
4: 2511
5: 4481
6: 12601
7: 8366
8: 21469
9: 1909
10: 46944
11: 54846
12: 59998
13: 60604
14: 59391

Yeah, I give up finding the code for this.

Today we have time-based background throttling. I wonder if we should also have count-based throttling, e.g. 10 tasks per 10 minutes or something like that?

Thoughts/ideas welcome.

I wonder how widespread this problem is. Ojan, do you happen to have some examples or some data?

No data. The only examples I know of are google products with chat: hangouts, gmail, inbox. I know there are others out there, but this is just the anecdata I run into with my own browsing.

The NextAction date has arrived: 2017-06-29