1515794 - Avoid constructing custom element and/or XBL binding code for <tree>s in browser.xul on DOMContentLoaded to avoid the associated overhead

Status: RESOLVED FIXED

(Firefox :: General, enhancement, P3)

Description

[:Gijs (out for now; he/him)]

Right now, profiles show that the connecting of the tree UA widget causes us to call _ensureColumnOrder in tree.xml, which requires constructing a boxobject for the tree, which trips webrender, which blocks the main process for a significant proportion of time (easily 120-250ms on my machine). This was previously tracked in bug 1508213. It's unclear if this has regressed or if there's just more optimization to be done, but we'll still pay a similar-ish cost for initializing webrender at a different point.

Either way, we should be able to avoid this by constructing trees at runtime instead of having them hardcoded in the markup.

Comment 1

[Florian Quèze [:florian]]

I this profile https://perfht.ml/2GTMeO1 this bug represents a third of the time it took to open a new browser window.

Comment 2

[:Gijs (out for now; he/him)]

(In reply to Florian Quèze [:florian] from comment #1)
> I this profile https://perfht.ml/2GTMeO1 this bug represents a third of the
> time it took to open a new browser window.

Seems that most of that is just that we're forcing the creation of a compositor and it uses sync IPC, which in this instance took a "long" time... but I expect we'd have to pay that cost somewhere else if we fixed this bug.

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Bot fail? This was on the right component.

Comment 4

[Marco Castelluccio [:marco]]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #3)

Bot fail? This was on the right component.

Yes, we are trying to assign 'General' to more specific components when possible (it is often possible). This was a bad result.

Comment 5

[Sylvestre Ledru [:Sylvestre]]

I am not convinced that Firefox::General can be the right component :)
Anyway, as a human, reading comment #0, I could have made the same call.

Comment 6

[Brian Grinstead [:bgrins]]

I think this was fixed as of Bug 1523957 / https://hg.mozilla.org/mozilla-central/rev/a6606e852767#l4.18. Can you confirm this can be closed?

Comment 7

[:Gijs (out for now; he/him)]

Yes, I don't see anything in the stats anymore.