"Concurrent code compilation is another step towards reducing latency in Chrome and is part of various ongoing efforts to deliver more responsive, smoother web applications," Google engineer Yang Guo said in a blog post describing the change.
That compilation step can eat up some processor cycles, though, so to minimize delays, V8 doesn't get too fancy about it – at least, not at first. The code is initially compiled in a very straightforward way, without spending much time on performance optimization.
But V8's compilation infrastructure – dubbed "Crankshaft" – is clever. Code that is executed often is actually compiled a second time after the application is already up and running, this time piling on the optimizations to ensure maximum performance.
With earlier versions of Chrome, the circled portion would have been all pause (click to enlarge)
The catch, for now at least, is that the revamped V8 is only available in the Chrome Beta channel. Google doesn't announce hard dates for when it plans to promote Chrome builds from Beta to Stable status, but if all goes well in its testing, we can assume that concurrent compilation will be enabled for all Chrome users within the next few months. ®