The v8 benchmark component deltablue has an overhead of 6% in the array push and pop routines and descendants.
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%
Comment on attachment 68980 [details] Patch to Allocate Minimal Space for Array() r=me
Curious if a larger number wouldn't be better. I assume you tested a variety of sizes? I wonder what V8 does here.
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>
All reviewed patches have been landed. Closing bug.
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).