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The Chrome javascript engine team is simply a beast.
I'm curious to see if they broke any code, like the IE engine did recently. For example, with loop-invariant code motion, what is legal in a language like C, may not be in Javascript (for same reason the IE DCE optimization was invalid).

I'd find it hard to believe that Goog would make the same mistake after all the hullaballoo, but I'd love to see it validated.

I'd like to have a guide for writing code that is easily optimized by V8 and similar engines. Having local variables is good, as far as I can tell, but it would be nice to have a full overview with dos and don'ts
"Having local variables is good"

Reading sentences like this scare me because it reminds me that some people don't know what the 'var' keyword means or think it's acceptable to shove everything in window or global.

The IE team didn’t break anything in shipping software, right? This is just an IE9 beta problem, presumably fixable before they ship a stable IE9?
Absolutely. It wasn't even beta, it was just a tech preview. If they didn't have bugs of that sort, they aren't pushing things hard enough.
Loop-invariant code motion is still legal in JS, and most dynamic languages, as is DCE. You just need to take into account the weird semantics of JS.

What the IE team got wrong was the assumptions they made about the semantics of the code that was optimized. If they had checked for the presence of a valueOf property, they could still have done the optimization.

Exactly. I'm not saying those opts aren't legal, but in cases that look legal in C, they're not legal in JS. And note, you can still do it in the presence of a custom valueOf method, as long as it doesn't have side effects (and thus of course loop-invariant itself).

In essence I'm asking if Google does in fact do this check, and does analysis to ensure that the valueOf method doesn't get written dynamically in the loop itself.

"...performance of JavaScript property accesses, arithmetic operations, tight loops..."

Does this mean Crankshaft includes a tracing JIT like Firefox? This layman speak confuses me.

Yes, look at the list of the four main components.
I don't think that says it uses a tracing compiler (naturally the terms are vague in this field, so I'm not certain). Their architecture looks much more like HotSpot than TraceMonkey.
It will be interesting to see how this optimization affects V8's memory profile (and how that in turn affects the currently slim memory profile of Node.js).
Looks like this Node patch includes Crankshaft: https://github.com/ry/node/commit/c30f1137121315b0d3641af6dc...
It will also be interesting to see if this improves performance of long running Node.js scripts.
When Chrome was released two years ago, I noticed a significant difference in speed. Nowadays I think the announcements JavaScript performance improvements is a bit overenthusiastic. The only real world benchmark mentioned in the article is that Gmail loads 12% faster. What JavaScript apps are constrained by performance and what are Crankshaft's effects on them?
I think the point of these optimizations is that they allow javascript-intensive applications to be developed that would otherwise have just been too slow.

In other words, they're paving the way for the future more so than trying to squeeze every last ounce of speed from current applications (which just happens to be a great side effect of their work).

Yeah, you won't see a lot of applications that benefit from these optimizations immediately because if there were any that would mean that they had been written before there was any device capable of running them.
I'm happy that the various javascript teams are developing towards where the web is going rather than where it is.

"A good hockey player plays where the puck is. A great hockey player plays where the puck is going to be." — Wayne Gretzky

I don't think the GP would disagree with you. I believe he was asking what specific apps benefit today (besides GMail which was mentioned in the blog).
Much web client JS is constrained by dom speed so this will only have an incremental effect. However, for node apps this willbe pretty significant.
> What JavaScript apps are constrained by performance and what are Crankshaft's effects on them?

Canvas and WebGL games.

unreal. how much theoretical headroom is left to optimize js compiler performance?

I had assumed we were reaching some theoretical upper-bound because all major frameworks were on par in terms of performance.

To a first approximation, my answer would be something like http://shootout.alioth.debian.org/u32/benchmark.php?test=all... .

That's not necessarily the whole answer and I imagine JS can't ever quite go that fast. But still....

> and I imagine JS can't ever quite go that fast

I'm not the most knowledgeable person on the subject, but from what i understand, there is no theoretical reason that JS couldn't go that fast. The two languages are more similar than they are different, even if JavaScript is quite more complex.

I remember Mike Pall saying something similar in an LTU thread some time ago.

Would this imply that Lua has reached some pinnacle of speed and can't go any faster? That seems to be a side effect of your statement.

I'm not familiar with Lua, beyond reading an article or two about it, but does its simplicity imply some sort of maximal efficiency? Are the developers behind Lua simply the best programmers in the world and already have everything figured out with regard to optimizing a JIT? I'm not arguing with you...it does seem like that's a reasonable goal for JavaScript JITs to strive for in the near future. But, it doesn't really answer the question of how much better performance can get (in JavaScript or Lua or any other language). Past performance is not necessarily indicative of future performance when so many people are working on the problem from so many angles.

I think http://shootout.alioth.debian.org/u32/benchmark.php?test=all... is probably a better ceiling. LuaJIT is fantastic and already generates better code than GCC in some cases, but in many others it does not.

There's no theoretical limit to how close a compiler can come to a programmer when it comes to generating machine code to do a particular well-defined task.

Javascript execution is very rarely the bottleneck on webpages. The bottleneck is almost 90% render speed of dom updates.
So - how long does it take for features to make their way into production? Am I reading the release calendar correctly in that it'll take 12 weeks from start of development to beta, and another 12 weeks from beta to stable?

It looks like Chrome 8 went stable on 12/2. So we'll see Chrome 10 in 4 months?

Chrome stable releases are every 6 weeks.

The releases are overlapped though, so we are testing v n+1 in beta while v n is in stable, and we are starting new feature development for v n+2 while v n is in stable.

Chrome 8 just went stable, and we've just started testing Chrome 9.

So crankshaft will either be 6 weeks from today (if it's in 9), or 12 weeks from now (if it's in 10).

I don't think it's been announced which it's targeted for.

HTH

Gmail really does seem to load in about half the time now in the Canary build.
OTOH this does not bode well for the future potential bloat in Gmail.
I've benchmarked Google Chrome 9.0.597.10 and 10.0.603.3 (with Crankshaft) and the latter is 30% faster. See the detailed results: http://dromaeo.com/?id=124912,124913
Has anyone got any experience using javascript/V8 as a scripting language for a C++ app? We currently use python with boost::python bindings, but are finding we have to limit the amount of python code, as it is too slow.
Have you looked into lua? It's a good embedded scripting language.

http://www.lua.org/

Ever looked into Cython? http://www.cython.org/

Sage (a open source replacement for matlab) uses it quite successfully for speeding up critical paths.

Thats essentially what Node.js is, although with a heavy focus on asynchronous operation.

Check out: https://www.cloudkick.com/blog/2010/aug/23/writing-nodejs-na...

Syntensity moved from Python to JavaScript as an embedded scripting language,

http://www.syntensity.com/toplevel/intensityengine/

worked out very well there.

Of course the real examples are... web browsers, which are C++ apps that are scripted by a JavaScript engine. Seems to work good there as well ;)

At Anybots, we built all the real-time robot code in Python with performance-critical bits in C++ wrapped using boost::python. Server code is in pure Javascript on Node.JS. I haven't tried to integrate C++ into Node, but it looks easy.
Next up, remove the 1.9GB max memory limit of V8 processes: http://code.google.com/p/v8/issues/detail?id=847
Will this have any effect on NodeJS?
I doubt it.

From what I understand, the significant improvements in speed come from Crankshafts tradeoff of compilation optimisation for startup speed. If your app is a for loop with 2 iterations that code path won't be heavily optimised as the interpreter would potentially be more spending more time compilation code than in execution of unoptimised code. It will therefore startup faster. However, hotspots (loops with 1,000 iterations, per se) will be heavily optimised.

This is great for websites as speed and responsiveness is perceived as startup time. You'll certainly notice a difference when using the Node as a scripting tool. However, most Node applications are long running servers executing the same code paths over and over. Its unlikely that Crankshaft is performing any extra optimisations, it is just changing when it performs these optimisations. However, if Crankshaft _is_ doing significantly more advanced optimisations (I don't know) then, yes, Node will benefit. Please correct me if I am wrong, I would love to be.

Sure, I would expect node.js to be an ideal environment for this type of hot code analysis, since servers written with it are typically long running vs. more transient web pages. Of course whether there are significant gains depends a lot on whether your server is CPU-bound or IO-bound.
This seems like it would be huge for the Node.js people. The next big milestone for V8 for node has to be the GC issues that have been wreaking havoc on node apps under high load.
Seems like it should.
Sounds like they borrowed the tracing idea from mozilla.
Not really. It's a well-known VM optimization technique.
They don't mention that they're tracing. I think they're just optimistically optimizing functions in hot loops.
I thought someone was actually developing a new kind of crankshaft for a real V8 engine....
Doesn't `Chromium Blog' and the URL give it away?