Bug 46664

Summary: 6% Array Push and Pop Overhead in v8-deltablue
Product: WebKit Reporter: Michael Saboff <msaboff>
Component: JavaScriptCoreAssignee: Michael Saboff <msaboff>
Status: RESOLVED FIXED    
Severity: Normal CC: ager, commit-queue, eric
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: All   
OS: OS X 10.6   
Attachments:
Description Flags
Patch to Allocate Minimal Space for Array() none

Michael Saboff
Reported 2010-09-27 15:25:55 PDT
The v8 benchmark component deltablue has an overhead of 6% in the array push and pop routines and descendants.
Attachments
Patch to Allocate Minimal Space for Array() (2.30 KB, patch)
2010-09-27 15:36 PDT, Michael Saboff 		no flags
DetailsFormatted DiffDiff
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Michael Saboff
Comment 1 2010-09-27 15:36:52 PDT
Created attachment 68980 [details] Patch to Allocate Minimal Space for Array() Changes the JSArray() constructor that takes an ArgList argument to allocate space for three elements when the ArgList is empty. This improves v8-deltablue by about 2.8%
Geoffrey Garen
Comment 2 2010-09-27 16:45:56 PDT
Comment on attachment 68980 [details] Patch to Allocate Minimal Space for Array() r=me
Eric Seidel (no email)
Comment 3 2010-09-27 18:49:12 PDT
Curious if a larger number wouldn't be better. I assume you tested a variety of sizes? I wonder what V8 does here.
WebKit Commit Bot
Comment 4 2010-09-27 18:52:54 PDT
Comment on attachment 68980 [details] Patch to Allocate Minimal Space for Array() Clearing flags on attachment: 68980 Committed r68469: <http://trac.webkit.org/changeset/68469>
WebKit Commit Bot
Comment 5 2010-09-27 18:52:58 PDT
All reviewed patches have been landed. Closing bug.
Michael Saboff
Comment 6 2010-09-28 10:04:48 PDT
In response to comment from eric@webkit.org, I tried values of 1 through 4. It appears that there is a knee at 3 as it was better than the other values. I suspect that the initialization overhead hurts as the value goes higher (the JSValue() constructor is called for each allocated element).
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