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M:N threading done right, at last?

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Aug 2, 2021

Replying to @pcwalton @bascule and 3 others

The new incarnation of SwitchTo, named User Managed Concurrency Groups, seems to be coming along well: lore.kernel.org/patchwork/cove There's still hope.

Patrick Walton

@pcwalton

Aug 3, 2021

If this becomes performance competitive with async I/O (I have no idea if it will be), then it'd be interesting to see the effect on the Rust ecosystem. Will sync I/O become popular again? Or will everyone stick with async because we've grown accustomed to the patterns?

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And where does io_uring fit in ?

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and

The main use case is completely replacing needing a thread pool for AIO hooked up to eventfd + epoll. It avoids a ton of context switches between threads, system calls, scheduling and other resource use. It's also essentially a generic system call multiplexer for I/O and events.

10:17 AM · Aug 3, 2021Twitter Web App

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and

If you want to use it properly rather than just as an AIO implementation, then you probably want to build around it rather than having portable code. If you want portable code not tied to the design of the API, then you're not going to be able to take advantage of properly.

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and

If you have plenty of spare CPU time + memory, you can get comparable performance as io_uring by adding more threads as needed until you're saturating NVMe performance regardless. It's extremely helpful anywhere needing fast AIO where CPU / memory are not sitting around unused.

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