But what sort of effect will this have on page rendering? Anyone in the know care to comment on the specifics?
edit: improvements to my shoddy wording.
Possibly not desktop performance at all since I believe GC is done in a separate thread and (from my understanding) you never wait on it, unless you are really memory constrained.
Could make a difference on IOS where I believe you actually don't have this GC memory scavenger thread.
Anyway, the source is quite readable and everyone working with WebKit on one level or another could benefit from taking a look. At the very least it gives you a feeling for the tremendous effort from a huge number of people that the WebKit project really is.
I would guess this is relevant only for GC in Safari, since it uses the WebKit JS engine, and not Chrome (which uses a completely different JS engine, V8).
It's also likely only a speedup in a specific GC benchmark. If it had helped in say the SunSpider benchmark, I'm pretty sure it would have been fixed a long long time ago.