[eyelidlessness]

It seems the “threading” mechanism depends on the browser’s own process model? As in, you’ll get another “thread” iff the browser creates a separate process for the cross-origin iframe?

That’s a clever hack where it works. For what it’s worth, it doesn’t seem to work on mobile Safari, at least judging by both examples slowing down at roughly the same rate. In which case, the “parallel” example is very slightly slower, presumably due to marginal overhead of the cross-frame mechanism.

[ashubham]

Yes correct. Safari/FF have shown positive intent to implement this FWIW.

[mr_toad]

They say they’re looking at implementing origin-agent-cluster. That doesn’t mean they’ll change their internal process model. There is no specification for how a browser runs processes. Even Chrome might decide to use threads instead of processes for iframes.

[ashubham]

Correct. A different thread is good too, as long as they are separate resources from the main DOM.