1132196 - Unresponsive for about 10 seconds due to restyle + flex reflow when loading http://codepen.io/chriscoyier/pen/ogWWPK

Status: RESOLVED WORKSFORME

(Core :: Layout, defect)

Description

[Markus Stange [:mstange]]

STR:
 1. Load http://codepen.io/chriscoyier/pen/ogWWPK
 2. Watch your browser freeze.

Comment 1

[Markus Stange [:mstange]]

Profile: http://people.mozilla.org/~bgirard/cleopatra/#report=c31c9f0a34dacb029fbe5f37646d49d63bce0daf

Comment 2

[Daniel Holbert [:dholbert]]

FWIW, this only hangs for ~1.5-2 seconds on my linux desktop, FWIW (not 10 seconds), while laying out the codepen "results" pane.

(Tested using both Nightly v38 & release v35; no significant difference between them.)

Still, it does render much more quickly in Chrome.

Comment 3

[Daniel Holbert [:dholbert]]

I think this is WORKFSORME these days; one of our flexbox perf improvements must've helped here, and now we're on-par with Chrome.

In particular:

• Here's a profile of me loading https://codepen.io/chriscoyier/full/ogWWPK in Nightly: https://share.firefox.dev/2C2yXAV . There's no noticeable delay from a usage standpoint (it loads in less than a second), and the biggest delay shown in the profile is a 297ms reflow.

• In Chrome, a profile of the same pageload shows a 307ms layout followed by a 114ms layout.

• So we seem to be doing at least as good as Chrome here, in terms of layout/reflow time.

Comment 4

[Daniel Holbert [:dholbert]]

Here's the Chrome profile that I recorded: https://share.firefox.dev/3dWYJER
(Their long layouts are reported as 308ms and 115ms - I had rounded down in comment 3 to be charitable, but our profiler UI accurately rounds up because there were large fractional parts.)