1942561 - 2.5 seconds spent in "Layout Cleanup" on a testcase that creates 300000 dropdown menus

Status: RESOLVED INVALID

(Core :: Layout, defect)

Description

[Mayank Bansal]

Attachment: Dropdowns_300000_1.html

Open the attached testcase
Enter 300000 number of dropdowns
Enter 1 as number of items in dropdown
Click on generate dropdowns
Wait for the dropdowns to be created
Reload the page using the reload button the toolbar

Profile: https://share.firefox.dev/42melNX (2.5s)

Maybe something to improve?

Comment 1

[Mayank Bansal]

:dholbert, you may have some opinion here given the ongoing work in bug 1939344 (and its dependencies)

Comment 2

[Daniel Holbert [:dholbert] (PTO until 2/24)]

In the profile, at first glance, it looks like ~all of our time is spent on deallocation code; I'm not seeing anything that's obviously wasted.

For me, Chrome seems maybe an order of magnitude slower than Firefox on this testcase -- both on creating the dropdowns which takes ~tens of seconds in Chrome (I didn't measure exactly how long), and on reloading the page which takes ~20 seconds in Chrome. So it's not obvious that there's much room for [or interop requirements for] improvement here.

--> Tentatively calling this "INVALID" since I can repro the described behavior (~2.5s delay for a reload) but it's not really a Firefox bug or something that needs fixing.

Comment 3

[Mayank Bansal]

Thanks Daniel for investigating!