Hacker News Reader

Comment by Rochus | Hacker News Reader

Apparently they compare their JIT with the LuaJIT interpreter. I would be impressed if their JIT was 30% faster on average than LuaJIT in JIT mode. The Graal/Truffle generated VMs are much faster (see e.g. http://software.rochus-keller.ch/awfy-bun-summary.ods).

View on HN

> Graal/Truffle generated VMs are much faster (see e.g. [link]).

Faster than what? I don’t see any mention of any kind of Lua in that table or in the page it mentions. It’d be awesome[1] if Graal could outdo LuaJIT on Lua, and I was initially excited to learn that it did, but I don’t see anything about that there.

[1] Or as awesome as it’s possible to be for something that Oracle evidently intends to patent to the gills, anyway.

You can e.g. use Node.js as a reference and compare with these results: https://github.com/rochus-keller/Oberon/blob/master/testcase.... LuaJIT with JIT on is usually factor two slower than Node.js and factor five slower than C/C++ in my measurements.

No, they also compare JIT to JIT and theirs is 30% slower. But it's only a baseline JIT and they'll have optimizing soon (tm).

It’s also a completely different class of JIT: a method-at-a-time one, not a tracing one. As I’ve mentioned in a thread some time ago, this is a very impressive project that is a JIT for Lua, but it has so little to do with LuaJIT’s architecture otherwise that calling it LuaJIT Remake feels actively misleading. It’s SpiderMonkey for Lua, if anything.

Ok, apparently I misinterpreted the text; it would be easier to unserstand if they used factors instead of percentages. Actually it's pretty close to LuaJIT in JIT performance, which calls into question both the use of manual assembler programming and the huge effort and complexity of the handmade tracing JIT. However, it is not yet clear to me whether there are other factors, so that, for example, the results on 32-bit architectures would be better for LuaJIT. Or maybe they profit of the fact that there are still a lot of operations in LuaJIT not supported by the JIT (such as FNEW, which is detrimental for all applications depending on closures), and their baseline JIT supports them in contrast.

Reply on news.ycombinator.com