RESOLVED FIXED291827
REGRESSION(281090@main): CSS grid performance regression 
https://bugs.webkit.org/show_bug.cgi?id=291827
Summary REGRESSION(281090@main): CSS grid performance regression
Tony Finch
Reported 2025-04-20 12:50:55 PDT
The web site https://lobste.rs recently changed its layout to use CSS Grid, and since then its performance in Safari has become extremely bad. It is much worse in recent versions of Safari. Example page illustrating the problem: https://lobste.rs/s/v7lsrv/two_years_rust On my Mac running Sonoma 14.6.1 (23G93) and Safari 17.6 (19618.3.11.11.5) this problem page takes about 3 seconds to render or reflow after the window is resized, and characters typed into the comment box take 2 seconds to appear. On iPad OS 18.3.2 it fails to render within a couple of minutes. On my Mac running Safari Technology Preview 217 (Safari 18.4, WebKit 19622.1.9.19.2) the problem page also fails to render within a reasonable length of time. After entering the URL, one core is pegged at 100% for about 230 seconds (nearly 4 minutes) before at last the page is rendered. This bug might be related to https://bugs.webkit.org/show_bug.cgi?id=269558
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Add attachment proposed patch, testcase, etc.
Tony Finch
Comment 1 2025-04-21 11:16:38 PDT
I understand Lobsters is being changed to work around this bug so I have saved a copy of page exhibiting the problem at https://web.archive.org/web/20250421180443/https://lobste.rs/s/v7lsrv/two_years_rust
Radar WebKit Bug Importer
Comment 2 2025-04-21 12:09:41 PDT
<rdar://problem/149704403>
Sammy Gill
Comment 3 2025-06-03 12:12:38 PDT
Pull request: https://github.com/WebKit/WebKit/pull/46269
EWS
Comment 4 2025-06-04 11:38:18 PDT
Committed 295826@main (8af27c463fdd): <https://commits.webkit.org/295826@main> Reviewed commits have been landed. Closing PR #46269 and removing active labels.
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