The team seems to be pretty focused on getting to be faster than Chrome/Safari. Great idea to have a simple goal, and a simple answer to whether they have achieved it or not.
Looking at their v8 bench speedup: from 0.7 ms to around 0.3 ms we get again 2.3, comparable with the simple loop measurement. But interestingly enough, Google's V8 gets its speed in a very different way, as my mentioned benchmark loop performs much worse in Chrome: 3.9 sec on Chrome 6.0.472, thats 4.4 times slower than ActionScript or Firefox Beta 4.
Can't get over how young the programmer team looks. Compared say, to Lars Bak who is 45-ish and working on V8... Whatever happened to the grizzled JIT writers?
The team's explanation: Right now, the performance tests
are run on a Mac, which means no IE. Also the tests rely on
a "shell" JS engine that runs in a command line. It doesn't
test browsers. We'll change that, eventually.
I do a lot of experiments around the edge of browser performance (and also regularly check other folks' demos in multiple browsers).
Benchmarks are not completely representative to "real world" performance. There are always some areas which work very well in particular browsers and areas in which some browsers are absolutely terrible.
You can get practically arbitrary order of browser performance by mixing "do-good" and "do-bad" tasks.
Subjectively, since recently Opera often feels faster than Chrome [1].
Not always, it's maybe 50/50 split, sometimes Chrome is faster, but in overall subjective experience Opera feels better (by a tiny bit).
I suspect it's because Chrome excels mainly at "behind-the-scene" more numerical type of tasks, while Opera is faster at more tangible "in-your-face" things like DOM manipulation / rendering / canvas.
Also, again subjectively, Opera's performance feels better "balanced". Chrome is crazy fast in some areas (see V8 benchmark), but slow/average in others. Opera is fast almost everywhere, so it has less bottlenecks.
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[1] More objectively, from my stuff which has numerically comparable performance:
(For example, "The benchmark starts with an array of 100,000 elements and removes 20 elements for each call. After 5000 calls, the calls become no-ops, and the benchmark then times those no-ops.")
Gah, I was about to say that Opera beats Chrome at Sunspider on my machine, but then realized I was still running Chrome 5. Just upgraded. Here are the Sunspider numbers on my machine:
You have to update your extension's manifest every time a new version of Firefox is out. It is possible that your extension's maintainers haven't included Firefox 4 in their list of whitelisted versions even though it may work. Provided you are sufficiently technical and wouldn't mind dealing with crashes, install Nightly Tester Tools (now renamed to something more officially iirc, but searching for Nightly Tester Tools should get you there) and try to disable the compatibility check and see if it works. Back up your profile first so you can just copy it over again if something breaks horrifically.
http://nightly.mozilla.org/js-preview.html
with my simple benchmark loop (two floating point additions per pass) and it's really better:
300M passes of loop, time in seconds:
0.88 Firefox 4b6
2.26 Firefox 3.6.6
which is approximately 2.5 times faster.
Now that particular loop executes at the same speed as ActionScript 3 (in Flash 10) with explicit typing. That's the big achievement for Mozilla.