Fil's Unbelievable Garbage Collector

Hmm, Fil-C seems potentially really important; there's a lot of software that only exists in the form of C code which it's important to preserve access to, even if the tradeoffs made by conventional C compilers (accepting large risks of security problems in exchange for a small improvement in single-core performance) have largely become obsolete.

The list of supported software is astounding: CPython, SQLite, OpenSSH, ICU, CMake, Perl5, and Bash, for example. There are a lot of things in that list that nobody is likely to ever rewrite in Rust.

I wonder if it's feasible to use Fil-C to do multitasking between mutually untrusted processes on a computer without an MMU? They're making all the right noises about capability security and nonblocking synchronization and whatnot.

Does anyone have experience using it in practice? I see that https://news.ycombinator.com/item?id=45134852 reports a 4× slowdown or better.

The name is hilarious. Feelthay! Feelthay!

> I wonder if it's feasible to use Fil-C to do multitasking between mutually untrusted processes on a computer without an MMU?

You could. That said, FUGC’s guts rely on OS features that in turn rely on an MMU.

But you could make a version of FUGC that has no such dependency.

As for perf - 4x is the worst case and that number is out there because I reported it. And I report worst case perf because that’s how obsessive I am about realistically measuring, and then fanatically resolving, perf issues

Fact is, I can live on the Fil-C versions of a lot of my favorite software and not tell the difference

> As for perf - 4x is the worst case and that number is out there because I reported it

I love the concept of Fil-C but I find that with the latest release, a Fil-C build of QuickJS executes bytecode around 30x slower than a regular build. Admittedly this is an informal benchmark running on a GitHub CI runner. I’m not sure if virtualization introduces overheads that Fil-C might be particularly sensitive to (?). But I’ve sadly yet to see anything close to a 4x performance difference. Perhaps I will try running the same benchmark on native non-virtualized x86 later today.

Also, so I am not just whining, my Fil-C patch to the QuickJS main branch contains a fix for an issue that’s only triggered by regex backtracking, and which I think you might have missed in your own QuickJS patch:

http://github.com/addrummond/jsockd/blob/main/fil-c-quickjs....

30x? Oof

I know that I regressed quickjs recently when I fixed handling of unions. It’s a fixable issue, I just haven’t gone back and fixed it yet.

I definitely don’t see 30x overhead on anything else I run.

But thanks for pointing that out, I should probably actually fix the union handling the right way.

(What’s happening is every time quickjs bit casts doubles to pointers, that’s currently doing a heap allocation. And it’s obviously not needed. The simplest compiler analysis would kill it. I just turned off the previous instance of that analysis because it had a soundness issue)