8cbef1dfc1
Add epoll-based non-blocking I/O and kernel-like mutexes: - src/io.rs: Complete epoll backend with timeout & error handling - src/mutex.rs: Fair mutex with waiter queues & parking integration - Enhanced scheduler to support synchronous I/O blocking - Comprehensive test suites for I/O (epoll) and mutex behavior - Documentation: LOOM.md concurrency model & README
85 lines
3.1 KiB
Markdown
85 lines
3.1 KiB
Markdown
# smarm
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> Silly Marks Abstract Rust Machine. A prototype green-thread actor runtime for Rust.
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Implements the core ideas in [`LOOM.md`](./LOOM.md): green-thread actors on a
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shared heap, scheduled cooperatively, communicating only by `Send` messages.
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Erlang's isolation model without Erlang's copying GC, Rust's zero-copy
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ownership transfers without async's function colouring.
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This is single-threaded for now — one scheduler, one OS thread. Multi-threaded
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scheduling is on the deferred list. The public API is shaped to match what the
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multi-threaded version will expose, so the migration shouldn't require source
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changes for downstream code.
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## What's here
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| Module | What it does |
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|--------------|------------------------------------------------------------------------|
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| `stack` | `mmap`'d growable stack with guard page; SIGSEGV on overflow |
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| `context` | `#[naked]` x86-64 context-switch shims, callee-saved regs only |
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| `preempt` | Allocator-driven preemption; `check!()` macro for no-alloc loops |
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| `pid` | `(index, generation)` PIDs; stale handles are detectable, not silent |
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| `actor` | Trampoline + `catch_unwind` boundary at the actor entry point |
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| `scheduler` | Run queue, slot table, spawn/join, parking, idle path |
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| `channel` | Unbounded MPSC channel; `recv` parks the actor |
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| `mutex` | `Mutex<T>` with mandatory timeout; FIFO waiters; parks the green thread |
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| `timer` | Min-heap of `(deadline, reason)`; `Sleep` and `WaitTimeout` reasons |
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| `io` | `block_on_io` for blocking work; `wait_readable`/`wait_writable` + `read`/`write` via epoll |
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| `supervisor` | `Signal::Exit` / `Signal::Panic` delivered to a parent actor's mailbox |
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## Quick taste
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```rust
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use smarm::{run, spawn, channel};
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run(|| {
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let (tx, rx) = channel::<i64>();
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let h = spawn(move || {
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for _ in 0..3 {
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let v = rx.recv().unwrap();
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println!("got {v}");
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}
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});
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for v in 1..=3i64 {
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tx.send(v).unwrap();
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}
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h.join().unwrap();
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});
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```
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## Layout
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```
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src/
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stack.rs context.rs preempt.rs pid.rs actor.rs
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scheduler.rs channel.rs mutex.rs timer.rs io.rs supervisor.rs
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lib.rs
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tests/
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per-module integration tests
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benches/
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primes.rs fan-out/fan-in compute, vs tokio current_thread
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LOOM.md design intent
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```
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## Building and running
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Standard Cargo. Requires Rust 1.95 or newer (the `#[naked]` attribute went stable
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in 1.88; we use a few unrelated post-1.88 features). x86-64 Linux only —
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ARM64 and macOS are on the deferred list because of the assembly shim and the
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epoll dependency.
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```sh
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cargo test # all tests
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cargo test --test mutex # one module
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cargo bench # primes benchmark vs tokio
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```
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## What's not here
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See the **Defer** section of `LOOM.md`. Notable absences: multi-threaded
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scheduler, supervisor restart-intensity caps, `join!` for handle groups,
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stack growth via remap, hierarchical timer wheel, fd-wait timeouts,
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`Signal::Timeout`. Each is mechanism we know how to add; none belongs in
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this iteration.
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