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Agreed. Defaulting to native threading gives developers so much more freedom. After all, M:N threading is just implemented on native threads anyway. You can sti

Agreed. Defaulting to native threading gives developers so much more freedom. After all, M:N threading is just implemented on native threads anyway. You can still do that if you want to. Rust isn't going to be a systems language used only for networking, so forcing a M:N threading model on it doesn't make sense. This change was necessary to keep Rust as a general use systems programming language.

dragonwriter 12y ago
> Rust isn't going to be a systems language used only for networking, so forcing a M:N threading model on it doesn't make sense. M:N threading decouples degree of concurrency from degree of parallelism, which is not desirable only for networking. And the old way wasn't about forcing M:N threading, it was about providing a common interface for concurrency independent of the relation of concurrency to parallelism in the backend implementation. I can understand the idea that that abstraction may have been too expensive, but I can't get behind the idea that 1:1 threading as the only thing supported in the standard library somehow provides more freedom for developers.
- dbaupp 12y ago
  Short-term it may look like there's less freedom since it's harder to use M:N threading (and 1:1 threading and M:N threading don't necessarily work perfectly together), but remember that the choice there is 1:1 threading with overhead and M:N threading with overhead. Long term, we can have libraries that provide M:N threading with minimal overhead; and also libraries that provide 1:1 & M:N together like the old std (with the associated overhead). That is, the programmer is getting more flexibility, just not right now (especially with Cargo, which makes it particularly easy to use external libraries). The team is trying to take a longer term view focusing std on safe interfaces to the OS primitives, which can then be used to build fancier/more abstract libraries more easily.
- keeperofdakeys 12y ago
  It's not like people are saying "Rust will never have M:N threading", it's that the current implementation didn't offer enough advantages for the disadvantages it brought. https://github.com/aturon/rfcs/blob/remove-runtime/active/0000-remove-runtime.md https://github.com/aturon/rfcs/blob/remove-runtime/active/00... Having done some things with libgreen threads myself, they really didn't give anything over proper threads (especially without segmented stacks). So I am curious how this will evolve in the future.

dragonwriter 12y ago

> Rust isn't going to be a systems language used only for networking, so forcing a M:N threading model on it doesn't make sense. M:N threading decouples degree of concurrency from degree of parallelism, which is not desirable only for networking. And the old way wasn't about forcing M:N threading, it was about providing a common interface for concurrency independent of the relation of concurrency to parallelism in the backend implementation. I can understand the idea that that abstraction may have been too expensive, but I can't get behind the idea that 1:1 threading as the only thing supported in the standard library somehow provides more freedom for developers.

dbaupp 12y ago
Short-term it may look like there's less freedom since it's harder to use M:N threading (and 1:1 threading and M:N threading don't necessarily work perfectly together), but remember that the choice there is 1:1 threading with overhead and M:N threading with overhead. Long term, we can have libraries that provide M:N threading with minimal overhead; and also libraries that provide 1:1 & M:N together like the old std (with the associated overhead). That is, the programmer is getting more flexibility, just not right now (especially with Cargo, which makes it particularly easy to use external libraries). The team is trying to take a longer term view focusing std on safe interfaces to the OS primitives, which can then be used to build fancier/more abstract libraries more easily.
keeperofdakeys 12y ago
It's not like people are saying "Rust will never have M:N threading", it's that the current implementation didn't offer enough advantages for the disadvantages it brought. https://github.com/aturon/rfcs/blob/remove-runtime/active/0000-remove-runtime.md https://github.com/aturon/rfcs/blob/remove-runtime/active/00... Having done some things with libgreen threads myself, they really didn't give anything over proper threads (especially without segmented stacks). So I am curious how this will evolve in the future.