Wow. My recent post about why Mozilla should adopt Native Client stirred up quite a storm. Some folks don't believe the web needs high-performance applications. Some are happy with whatever APIs browsers expose. I disagree with these points, but I can respect them.

Most surprisingly, several respondents had simply untrue objections to Native Client, so I'd like to clear up their misconceptions. Then I will make recommendations to the Native Client team on how to fix their perception problems.

If you want to spend some minutes and learn about Native Client and LLVM from the horse's mouth, watch this video.

Misconceptions about Native Client

Native Client implies x86

False. Originally, Native Client was positioned as an x86 sandbox technology, but now it has a clear LLVM story, with x86-32, x86-64, and partially-implemented ARM backends. Portability is a key benefit of the web, and Google understands this.

Native Client is complicated

True, it's certainly not a trivial amount of code. But compare the amount of code in NativeClient vs. Mozilla's JavaScript engine:

$ wc -l native_client/src/**/*.{c,h,cc}
155082 total
$ find mozilla-central/js/src -path '*tests*' -prune -o \( -iname '*.c' -o -iname '*.cc' -o -iname '*.h' -o -iname '*.cpp' \) -print0 | wc -l --files0-from=-
363471 total

NativeClient is at least on the same order of complexity as a modern JavaScript engine, and since it already provides performance within 5% of native code, I'd guess it's less susceptible to change.

Native Client / LLVM is not an open standard

I empathize with this concern, but Flash isn't an open standard and it sees wide adoption. The difference between Flash and Native Client is that Native Client / LLVM is open source and could easily become an open standard.

Native Client is insecure

Native Client was designed to be a secure x86 sandbox. Under the assumption that its basic security model is sound, the question then becomes "how large is the attack surface and how likely is it to be broken?" Given the amount of code in a modern web browser and JavaScript JIT, I don't see how Native Client is any worse.

With a little more work, JavaScript will perform at the same level as native code

I'm not informed or involved enough to claim JavaScript can never be as fast as native code. However, I have my doubts. A friend was working on a Monte Carlo Go AI, and he initially wrote his algorithm in JavaScript. Monte Carlo requires simulating a large number of game states, and a naïve port of his JavaScript to C++ gave a 100x performance improvement.

Check out my skeletal animation benchmark, where the JavaScript JITs need another 10x to compete with native code.

Even if JITs can match native code in some benchmarks (and I hope they do), performance across browsers will depend on the particulars of the JIT implementation. Native Client, at least for pure computation, would perform the same in every browser.

We can simply compile languages like Haskell, Python, and C to optimized JavaScript and let the JIT sort it out.

There are some attempts to use JavaScript as a backend for other language implementations, but they rarely perform well. For example, a CPython compiled to JavaScript via LLVM/Emscripten runs about 30x slower than a native build in Chrome, and 200x slower in Firefox 4 beta 8.

I've heard the argument for an RPython-like statically-analyzable subset of JavaScript that browsers could run very efficiently. This subset could operate as a defacto bytecode, and Emscripten could compile LLVM to it with minimal performance loss. It's possible this could work, but directly exposing LLVM seems more fruitful.

Red Herring Arguments

JavaScript is easier to develop with than native languages

Sure, but that doesn't mean native languages don't have a purpose. My hypothesis is that there are problems for which JavaScript is not and will not be suited, and that exposing the native power of the machine is better for application developers, and thus the web.

Binaries are obscure

Minified JS isn't human-readable either, but machines can reconstruct both. Drdaemon nails it in his comment


"If you want native performance, just download software or install a plug-in!"

While this sentiment reflects today's reality, it doesn't reflect trends on the web. Web applications continue to supplant desktop applications. Google Docs, Creately, Pivotal Tracker, Gmail, Mockingbird, and all of the games on Facebook are examples where I would have used a desktop application in the past. It seems that, whenever browsers provide new capabilities, applications consume them. Why would that trend stop now?

Recommendations to the Native Client team

  1. Get a move on! Enable it by default! More flashy demos!
  2. Reposition Native Client as a portable technology and make sure it's clear that LLVM is key to its strategy.

Finally, NativeClient is still new. I expect it will be some time before it's solid enough to rely on for production use. That said, it has the potential to disrupt the desktop operating system and I'm excited for a future where all software is web-based.