Firefox PerfStats feature mask needs to be updated to support 64bit mask

[acreskeyMoz]

Have you read the documentation?

• Yes, I've read the how to make a reproducable bug guide
• Yes, I've read the how to debug my script guide

URL

https://www.anysite.com

What are you trying to accomplish

We currently initialize the Firefox PerfStats (internal timing metrics) with a 32-bit feature mask, 0xFF_FF_FF_FF meaning collect all metrics.

browsertime/lib/core/engine/command/perfStats.js

Line 29 in 89c2ec6

async start(featureMask = 0xFF_FF_FF_FF) {

However, Firefox has since upgraded to a 64-bit feature mask, so we want to pass in
0xFFFF_FFFF_FFFF_FFFF to collect all metrics.

What browser did you use?

Firefox

How to reproduce

Collect PerfStats and observe that the last ones are all zero.

Log output

[acreskeyMoz]

Patch incoming.

[mstange]

JavaScript cannot represent this integer.

> (0xFFFF_FFFF_FFFF_FFFF).toString(16)
"10000000000000000" 

[acreskeyMoz]

JavaScript cannot represent this integer.

> (0xFFFF_FFFF_FFFF_FFFF).toString(16)
"10000000000000000" 

Ah, maybe that's why the linter wasn't happy.

This bigInt is valid though, right?
0xFF_FF_FF_FF_FF_FF_FF_FFn

https://github.com/sitespeedio/browsertime/pull/2314/files

[mstange]

Ah yes, a BigInt would work. But then we also have to fix ChromeUtils.setPerfStatsCollectionMask on the Firefox side to accept BigInts.

[acreskeyMoz]

Hmm, that may be tricky?

https://searchfox.org/mozilla-central/rev/78884344be27b9033bcea5660e0214477567a899/dom/chrome-webidl/ChromeUtils.webidl

It's not clear to me how we would express BigInt in webIdl, but maybe I'm missing something
https://firefox-source-docs.mozilla.org/dom/webIdlBindings/index.html

[mstange]

I don't know the answer, this is a question for our DOM team

[acreskeyMoz]

From mgaudet:

https://webidl.spec.whatwg.org/#idl-bigint

[mgaudet]

I may have spoken too soon: https://bugzilla.mozilla.org/show_bug.cgi?id=1764326

[dpalmeiro]

This is fixed now. We are using a string of features now.