1950269 - Testcase from bug 1945382 spends superlinear time "Layout cleanup" with reloading the page after generating N stylesheets (N=100k and above)

Status: VERIFIED FIXED

(Core :: CSS Parsing and Computation, enhancement)

Description

[Mayank Bansal]

Open the attached testcase. (Original "nested stylesheet_no BLOB" from bug 1945382)
Enter 100k , 200k, 300k and press enter
Wait for the stylesheets to get generated. May take a few 100ms which is amazing!
Reload the page using F5

100K: https://share.firefox.dev/4gRUHgA (3s)
200K: https://share.firefox.dev/3CSyZeA (11.6s)
300K: https://share.firefox.dev/3XiW5C1 (36s + 30s)

Maybe something to improve?

Comment 1

[Mayank Bansal]

Attachment: nested stylesheet_no BLOB.HTML

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1950269 - Optimize removing sheets from the end. r=#style

Removing from the front is expensive anyways because it reallocates the
array.

Comment 3

[Mayank Bansal]

Another case is to enter 100k and generate the stylesheets. Then without reloading, enter 1 and press enter.

100K

• Nightly: https://share.firefox.dev/4gYaxpO (6.5s)
• Chrome: https://share.firefox.dev/3D9YPKZ (200ms)

200K
Nightly: https://share.firefox.dev/41bLDgJ (40s)
Chrome: https://share.firefox.dev/435Cbhw (340ms)

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0d3bad538131
Optimize removing sheets from the end. r=firefox-style-system-reviewers,tlouw

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/0d3bad538131

Comment 6

[Mayank Bansal]

300K
Close the tab: https://share.firefox.dev/4kkCIlK (115ms)
Reloading the tab: https://share.firefox.dev/41ihRXB (35s around CC)

So the time spent in Layout/style is basically 0 now. The time spent in CC remains. . Not sure if a bug should be filed for the CC times.
But anyway, this bug is definitely fixed. Thanks Emilio!