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I’d not heard the term fiber before react reworked their framework around it. Is it a more general thing, and is there a good resource to learn about the theory

by aidos 7y ago

I’d not heard the term fiber before react reworked their framework around it. Is it a more general thing, and is there a good resource to learn about the theory?

htfy96 7y ago
Personally I recommend Distinguishing coroutines and fibers (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4024.pdf http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n402...) In short: - The key difference between fibers and kernel threads is that fibers use cooperative context switching - When a coroutine yields, it passes control directly to its caller (or, in the case of symmetric coroutines, a designated other coroutine). - When a fiber blocks, it implicitly passes control to the fiber scheduler. Coroutines have no scheduler because they need no scheduler
- Waterluvian 7y ago
  Is that kind of like how gevent for Python works? I thought they were coroutines but there's a scheduler, I think.
  - icebraining 7y ago
    Fibers can be built (and according to the paper, in C++ Boost they are) on top of coroutines, and that's essentially what both gevent and asyncio do.
scottlamb 7y ago
I don't think "fiber" has a universally agreed definition, which makes these things super confusing to read without clarification. It's hard to come up with a good definition and stick to it because people keep coming up with new variations. An interesting case is a different Google fiber library, not open-sourced but described in a public talk. [1] Real kernel threads but (mostly) scheduled in userspace via new syscalls [2] that suspend the current thread and unsuspend a userspace-chosen other thread. The idea is that most of the overhead of kernel threads is the scheduling and userspace has the ability to make a quick good choice. [3] Thus you can get most of the CPU performance of an async implementation but the relatively easy-to-read callback-free code of a threaded implementation. Anyway, people can disagree on what to call such a combination. [1] https://www.youtube.com/watch?v=KXuZi9aeGTw https://www.youtube.com/watch?v=KXuZi9aeGTw [2] the rseq stuff described in that talk has been upstreamed [4] but the switchto stuff still hasn't. [3] I'm not sure if the performance argument is as strong since the Meltdown/Spectre mitigations added to the performance cost of any syscall. [4] https://www.efficios.com/blog/2019/02/08/linux-restartable-sequences/ https://www.efficios.com/blog/2019/02/08/linux-restartable-s...
magicalhippo 7y ago
Not sure about the term, but I know Windows has had them for almost two decades[1], so hardly a newfangled concept. Here's[2] a fun/interesting 15 year old blog post explaining some of the use cases and pitfalls of using Win32 fibers. [1]: https://jeffpar.github.io/kbarchive/kb/128/Q128531/ https://jeffpar.github.io/kbarchive/kb/128/Q128531/ (CreateFiber) [2]: https://docs.microsoft.com/en-us/archive/blogs/larryosterman/why-does-win32-even-have-fibers https://docs.microsoft.com/en-us/archive/blogs/larryosterman...
eps 7y ago
"Fibers" is a term for manually-scheduled threads that was used in Windows at least since Windows 2000. Niche feature, but it was fully documented and all.

by aidos 7y ago

I’d not heard the term fiber before react reworked their framework around it. Is it a more general thing, and is there a good resource to learn about the theory?

htfy96 7y ago

Personally I recommend Distinguishing coroutines and fibers (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4024.pdf http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n402...) In short: - The key difference between fibers and kernel threads is that fibers use cooperative context switching - When a coroutine yields, it passes control directly to its caller (or, in the case of symmetric coroutines, a designated other coroutine). - When a fiber blocks, it implicitly passes control to the fiber scheduler. Coroutines have no scheduler because they need no scheduler

Waterluvian 7y ago
Is that kind of like how gevent for Python works? I thought they were coroutines but there's a scheduler, I think.
- icebraining 7y ago
  Fibers can be built (and according to the paper, in C++ Boost they are) on top of coroutines, and that's essentially what both gevent and asyncio do.

scottlamb 7y ago

I don't think "fiber" has a universally agreed definition, which makes these things super confusing to read without clarification. It's hard to come up with a good definition and stick to it because people keep coming up with new variations. An interesting case is a different Google fiber library, not open-sourced but described in a public talk. [1] Real kernel threads but (mostly) scheduled in userspace via new syscalls [2] that suspend the current thread and unsuspend a userspace-chosen other thread. The idea is that most of the overhead of kernel threads is the scheduling and userspace has the ability to make a quick good choice. [3] Thus you can get most of the CPU performance of an async implementation but the relatively easy-to-read callback-free code of a threaded implementation. Anyway, people can disagree on what to call such a combination. [1] https://www.youtube.com/watch?v=KXuZi9aeGTw https://www.youtube.com/watch?v=KXuZi9aeGTw [2] the rseq stuff described in that talk has been upstreamed [4] but the switchto stuff still hasn't. [3] I'm not sure if the performance argument is as strong since the Meltdown/Spectre mitigations added to the performance cost of any syscall. [4] https://www.efficios.com/blog/2019/02/08/linux-restartable-sequences/ https://www.efficios.com/blog/2019/02/08/linux-restartable-s...

magicalhippo 7y ago

Not sure about the term, but I know Windows has had them for almost two decades[1], so hardly a newfangled concept. Here's[2] a fun/interesting 15 year old blog post explaining some of the use cases and pitfalls of using Win32 fibers. [1]: https://jeffpar.github.io/kbarchive/kb/128/Q128531/ https://jeffpar.github.io/kbarchive/kb/128/Q128531/ (CreateFiber) [2]: https://docs.microsoft.com/en-us/archive/blogs/larryosterman/why-does-win32-even-have-fibers https://docs.microsoft.com/en-us/archive/blogs/larryosterman...

eps 7y ago

"Fibers" is a term for manually-scheduled threads that was used in Windows at least since Windows 2000. Niche feature, but it was fully documented and all.