4 ms·

Rust is really great, but I feel like you are overselling it a bit here: - async/await is available in the nightly version of Rust (1.39), but not in the stabl

Rust is really great, but I feel like you are overselling it a bit here: - async/await is available in the nightly version of Rust (1.39), but not in the stable version (1.37). - 1:1 threading is not strictly equivalent to M:N threading (the main practical difference being that the stack size per OS thread is larger than the stack size per goroutine). Writing that "Rust has broadly the same concurrency support" is misleading right now. But it could be true in a near future.

pcwalton 7y ago
The features that each language offers are the same: threads, channels, and blocking I/O (though Rust has more features for safe concurrency--Rust prevents data races statically, while Go is not even memory safe in the presence of such races). What is different is the performance characteristics. In some cases, M:N will be more efficient; in some cases, 1:1 will be. But just as I wouldn't say Go is lacking FFI features because M:N makes cgo slow, I wouldn't say Rust is lacking concurrency features.
- ngrilly 7y ago
  > blocking I/O Rust I/O are strictly similar to Go when using 1:1 OS threading, but become conceptually different when using async/await. > Rust has more features for safe concurrency--Rust prevents data races statically, while Go is not even memory safe in the presence of such races Agreed. That's a big advantage of Rust. > What is different is the performance characteristics. Performance is a feature. It's significant enough to justify using one language or the other depending on the project at hand. > In some cases, M:N will be more efficient; in some cases, 1:1 will be. The main advantage of the M:N model, compared to the 1:1 model, is the memory usage, because each goroutine starts with a small stack (a few kB). It makes possible to start a larger number of M:N goroutines than 1:1 threads. > But just as I wouldn't say Go is lacking FFI features because M:N makes cgo slow, I wouldn't say Rust is lacking concurrency features. Go's FFI works but is slow. It's a well known fact. Rust's concurrency story is not stabilized yet (areweasyncyet.rs). It's a fact too. I don't see a problem with acknowledging both :)
  - majewsky 7y ago
    > The main advantage of the M:N model, compared to the 1:1 model, is the memory usage, because each goroutine starts with a small stack (a few kB). Rust's async-fns compile into state machines, so they only allocate exactly the number of bytes that they need.
    - ngrilly 7y ago
      I know. I was writing about the 1:1 model without async/await :)

pcwalton 7y ago

The features that each language offers are the same: threads, channels, and blocking I/O (though Rust has more features for safe concurrency--Rust prevents data races statically, while Go is not even memory safe in the presence of such races). What is different is the performance characteristics. In some cases, M:N will be more efficient; in some cases, 1:1 will be. But just as I wouldn't say Go is lacking FFI features because M:N makes cgo slow, I wouldn't say Rust is lacking concurrency features.

ngrilly 7y ago
> blocking I/O Rust I/O are strictly similar to Go when using 1:1 OS threading, but become conceptually different when using async/await. > Rust has more features for safe concurrency--Rust prevents data races statically, while Go is not even memory safe in the presence of such races Agreed. That's a big advantage of Rust. > What is different is the performance characteristics. Performance is a feature. It's significant enough to justify using one language or the other depending on the project at hand. > In some cases, M:N will be more efficient; in some cases, 1:1 will be. The main advantage of the M:N model, compared to the 1:1 model, is the memory usage, because each goroutine starts with a small stack (a few kB). It makes possible to start a larger number of M:N goroutines than 1:1 threads. > But just as I wouldn't say Go is lacking FFI features because M:N makes cgo slow, I wouldn't say Rust is lacking concurrency features. Go's FFI works but is slow. It's a well known fact. Rust's concurrency story is not stabilized yet (areweasyncyet.rs). It's a fact too. I don't see a problem with acknowledging both :)
- majewsky 7y ago
  > The main advantage of the M:N model, compared to the 1:1 model, is the memory usage, because each goroutine starts with a small stack (a few kB). Rust's async-fns compile into state machines, so they only allocate exactly the number of bytes that they need.
  - ngrilly 7y ago
    I know. I was writing about the 1:1 model without async/await :)