Firefox Gets Massive JavaScript Performance Boost

monkeymonkey writes "Mozilla has integrated tracing optimization into SpiderMonkey, the JavaScript interpreter in Firefox. This improvement has boosted JavaScript performance by a factor of 20 to 40 in certain contexts. Ars Technica interviewed Mozilla CTO Brendan Eich (the original creator of JavaScript) and Mozilla's vice president of engineering, Mike Shaver. They say that tracing optimization will 'take JavaScript performance into the next tier' and 'get people thinking about JavaScript as a more general-purpose language.' The eventual goal is to make JavaScript run as fast as C code. Ars reports: 'Mozilla is leveraging an impressive new optimization technique to bring a big performance boost to the Firefox JavaScript engine. ...They aim to improve execution speed so that it is comparable to that of native code. This will redefine the boundaries of client-side performance and enable the development of a whole new generation of more computationally-intensive web applications.' Mozilla has also published a video that demonstrates the performance difference." An anonymous reader contributes links the blogs of Eich and Shaver, where they have some further benchmarks.

Comments

Re:As fast as C code???

[Anonymous Coward]

Correct me if I'm wrong, but generally speaking, I was always under the impression that, as an interpreted language, javascript will never be able to run 100% as fast as natively compiled C code.

Well, it has a JIT compiler, so that would transform it into bytecode essentially. It's the reason why C# is as fast as C code, because it too has a JIT. Google JIT :)

Re:As fast as C code???

[Bjarke Roune]

The optimization in the story is to compile parts of code written in Javascript. So when using this optimization, the Javascript is only partly interpreted, and if the compiled part is the part that takes up most of the runtime, then the Javascript could conceivably be something like the speed of natively compiled C.

Re:As fast as C code???

[Rockoon]

The amount of ignorance in this community is quite disturbing. I suspect that part of the cause is the unchecked pro-c religion, which always begins "C as faster than ...."

Clue phone guys. Ring. Ring.

C is a high level language and like all high level languages it can either be compiled, interpreted, or even translated. JavaScript is no different than C and can also also be compiled, interpreted, or even translated. There is nothing special about the C language that makes it inherently faster than other languages. C itself is a derivation of the language BCPL, whos shortcomming was a lack of datatypes. The design goal of these language syntaxes was parsing with minimal overhead because RAM was in short supply in those days. C was not designed to be "faster" than anything.

C is commonly mistaken to be superior because the most popular C compilers are commonly more advanced than the compilers of other languages due to simple supply and demand metrics. C is more popular, so its compilers have traditionally gotten more development effort. C itself isnt special beyond its popularity.

Fast as C but uses lots more memory

[CustomDesigned]

In general, JIT systems can really provide CPU performance near C speed, or even faster for some benchmarks, once the application gets going. The catch is that you pay two penalties: startup time and memory. Lots of memory: for keeping stats on what needs compiling, trampolines to call in and out of the interpreter vs. JIT native code, and the native code *plus* the byte code.

Even dynamic languages like Python can have a JIT - it specializes a function for various combinations of argument types, and then provides a catchall generic version for general objects. The catchall version is not much faster than the interpreter, usually (in fact it could *be* the interpreter), but the specialized versions can be much, much faster. (Also blocks can be specialized within any of the function versions.) But all those specialized versions take up memory. So the JIT keeps stats and tries to make only the ones that really help.

Re:Fast as C but uses lots more memory

[Mithrandir]

What's interesting is LLVM and .NET, where you can run C/C++ code in an interpreted/JIT-compiled environment. Potentially, with the optimizations mentioned above, you could have C code running in a virtual machine that's faster than statically-compiled C code.

HP did a lot of research on this about 4-5 years ago where they proved this was exactly the case. Do some googling for HP's Dynamo project. Real runtime knowledge of exactly what is being used and when leads to better optimistaion than static optimisation.

Re:As fast as C code???

[cbrocious]

Well, you're on the right trail, but not quite right. The key difference between Javascript and C, from an optimization standpoint, is the type system. The overhead of dynamic types is quite immense even at its most optimal. I suggest looking into the architecture of the DLR -- it really shows the key problems behind compiling dynamic languages and how they're being solved.