1685082 - Chrome refreshes news sites ~2x faster than Firefox

Status: NEW

(Core :: JavaScript Engine, defect, P2)

Description

[Bas Schouten (:bas.schouten)]

Refreshes feel like a fairly common thing to do on news websites. For some reason on my machine Chrome refreshes cnn.com (which is particularly slow) almost 2x faster than Firefox. Here are profiles, with times between hitting refresh and things 'mostly' being rendered:

Firefox (~3s): https://share.firefox.dev/2Lo1dT2

Chrome (~1.5s): https://share.firefox.dev/3rUQf8l

On FoxNews

Firefox (~1s): https://share.firefox.dev/2KWyHIC

Chrome (~0.6s): https://share.firefox.dev/396wYbo

Possibly I'm missing something but this feels like poorer responsiveness to be subjectively.

Comment 1

[Bas Schouten (:bas.schouten)]

It was brought to my attention this may be related to bug 1468476, although I'm not certain, but this bug has been lingering for 2 years as well.

Comment 2

[Bas Schouten (:bas.schouten)]

We seem to be spending roughly 50% of our time compiling/parsing things which feel to me like they probably didn't change with the refresh, any idea why the bytecode cache isn't kicking in here?

Comment 3

[Ted Campbell [:tcampbell]]

For bytecode cache to kick in now, we must successfully load (js text) from Necko at least 4 times, then the page must hit idle, then we must flush back to necko successfully.

Bug 1670403 is the work to use Stencil to remove these restrictions. The bytecode format will no longer require extra translation overhead, and we'll be able to decouple bytecode cache read/write from the actual DOM Document.