Resize the browser window with fast/multicol/float-multicol.html loaded. It is very very slow. The old multicolumn code is much faster. There is a bit more precision to the balancing with the new code, but I'm not convinced it's worth the performance cost. The latter is probably (just a guess) doing way more relayouts to improve the accuracy.
<rdar://problem/16656291>
In principle, it shouldn't have to do a lot more relayouts than the number of columns you have (unless you have a bug). I see that your test case has floats, and there's a bug in the new implementation in this regard. I reported it in Blink [1], and I have submitted a patch [2]. [1] https://code.google.com/p/chromium/issues/detail?id=361551 [2] https://codereview.chromium.org/242203003/
(In reply to comment #2) > In principle, it shouldn't have to do a lot more relayouts than the number of columns you have (unless you have a bug). I see that your test case has floats, and there's a bug in the new implementation in this regard. I reported it in Blink [1], and I have submitted a patch [2]. > > [1] https://code.google.com/p/chromium/issues/detail?id=361551 > [2] https://codereview.chromium.org/242203003/ I'll look into merging this (see my email to you though that I consider tall-float1.html to be an invalid test case, so I'm not going to merge that). tall-float1.html doesn't pass in WebKit, since we properly handle the case where you don't create columns and don't establish a block formatting context in that case.
I verified that the fix for 361551 does stop the assertion and resolve the performance issue with this test case, so: \0/
Created attachment 229815 [details] Patch
Attachment 229815 [details] did not pass style-queue: ERROR: Source/WebCore/rendering/RenderBlock.cpp:1475: Weird number of spaces at line-start. Are you using a 4-space indent? [whitespace/indent] [3] Total errors found: 1 in 8 files If any of these errors are false positives, please file a bug against check-webkit-style.
I didn't mean to include tall-float1.html, so just ignore that part.
Comment on attachment 229815 [details] Patch Looks good.
Landed in r167602. Note EWS is going to choke on tall-float1.html, but I didn't land that, so it should be fine.