Is Rust available on the platforms Linux targets? The kernel community won't react fondly to tries to restrict the target support. I'd expect a justified rant with lots of insults at intellect and sanity, if need be.
Is Rust well-understood, both by the users and the toolchain developers? How many independent compilers are there for Rust? What architectures do they support?
I'm not implying that Rust isn't suitable for Linux, but it has open issues, that prevent usage right now. Rust and it's core ecosystem have a lot of churn, and still feel like a rather early work-in-progress. One example not mentioned is the Rust language server and its integration with consumers.
Another issue I've seen with rust (benchmarks) that's rarely talked about is memory usage, which is pretty important in a kernel. Sometime it only uses a little more memory, but quite often it will use twice as much and occasionally an order of magnitude more.
To be fair these benchmarks are aiming for speed, but the c baseline typically produces faster code with less memory, so it may very well be a case of TANSTAAFL.
I don't see how it necessarily must be TANSTAAFL. Maybe Rust is indeed suited for being zero-cost in memory and speed performance compared to C, but the toolchain isn't there yet.
We use jemalloc by default, which does its own caching. A closer comparison would be to use the system allocator, or make the C code use jemalloc as well.
Oh, I'm not saying Linus would accept Rust code in the kernel at all; I don't think he should for a variety of reasons, including the ones you're talking about. That wasn't what I was responding to, though.
Is Rust well-understood, both by the users and the toolchain developers? How many independent compilers are there for Rust? What architectures do they support?
I'm not implying that Rust isn't suitable for Linux, but it has open issues, that prevent usage right now. Rust and it's core ecosystem have a lot of churn, and still feel like a rather early work-in-progress. One example not mentioned is the Rust language server and its integration with consumers.
I cheer for Rust, and hope for solid progress.