Bug 19369

Summary:	GC problem causes incremental degradation of execution speed
Product:	WebKit	Reporter:	Arthur Langereis <puurtuur>
Component:	JavaScriptCore	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED DUPLICATE
Severity:	Normal	CC:	ap, barraclough
Priority:	P2
Version:	528+ (Nightly build)
Hardware:	Mac
OS:	OS X 10.5
URL:	http://www.geocities.com/SiliconValley/7116/jv_bench.html

Arthur Langereis

Reported 2008-06-03 05:09:55 PDT

I was testing the new SquirrelFish engine and come upon this very old test page via a speed comparison page on codinghorror.com. The page has a few tests, all but one of which ran fine, the mb100 test was in comparison very slowly, about 0.7sec per run. Now each time I reloaded the page, 0.3sec of execution time was added permanently to the total time taken by this test, not any of the other ones, after a couple of reloads the test took about 2.5sec to complete, while the others ran unchanged. I extracted the test code and put it in a new file and tried that, the results stayed the same, the extracted test page is here: http://xfinitegames.com/safari/mb100.html After some deliberation on webkit with olliej I closed my tabs and the window and reran the test and the time taken was reduced to 300ms. Then I quit and reran the test and it took 94ms. I only had two tabs open, one the codinghorror page and the other were the results of the sunspider test I had performed a bit earlier. It was suggested that that had caused garbage build-up that for some reason this particular test was very vulnerable to. I hope the problem is clear enough, for more info mail me. On #webkit I discussed this with olliej.

Attachments
Add attachment proposed patch, testcase, etc.

Alexey Proskuryakov

Comment 1 2008-06-03 05:27:12 PDT