Issue #17059 has been updated by ko1 (Koichi Sasada).

Status changed from Open to Rejected

> Since the scheduler now have other registration control including rb_io_wait_readable and rb_io_wait_writable are introduced in the current Scheduler.
> I would try to use these methods to deal with the registration then, and replace the IO.select in the Scheduler#run for performance.

I'm not sure what is your idea, but at least I reject this ticket because `IO.select` is not good place to use `epoll`.

Maybe design Ruby-level event handling API and use it by scheduler is the best.

```ruby
s = IO::Selector
s.add(io1, 'r')
s.add(io2, 'w')
s.add(io3, 'rw')
s.wait #=> ready io array
```

for example.


----------------------------------------
Feature #17059: epoll as the backend of IO.select on Linux
https://bugs.ruby-lang.org/issues/17059#change-87097

* Author: dsh0416 (Delton Ding)
* Status: Rejected
* Priority: Normal
----------------------------------------
Current Ruby's `IO.select` method calls POSIX `select` API directly. With the new non-blocking scheduler, this may be the bottleneck of the I/O scheduling. For keeping the backward compatibilty of the current `IO.select` methods, a proposal may be to create a "duck" `select` which uses the `epoll_wait` as the backend.

One tricky part is that the `fd_set` described in POSIX is write-only, which means it is impossible to iterate for generating the `epoll_event` argument for `epoll_wait`. But similar to the large-size select situation, we could define our own `rb_fdset_t` struct in this case, and implement the following APIs.

```
void rb_fd_init(rb_fdset_t *);
void rb_fd_term(rb_fdset_t *);
void rb_fd_zero(rb_fdset_t *);
void rb_fd_set(int, rb_fdset_t *);
void rb_fd_clr(int, rb_fdset_t *);
int rb_fd_isset(int, const rb_fdset_t *);
void rb_fd_copy(rb_fdset_t *, const fd_set *, int);
void rb_fd_dup(rb_fdset_t *dst, const rb_fdset_t *src);
int rb_fd_select(int, rb_fdset_t *, rb_fdset_t *, rb_fdset_t *, struct timeval *);
```

TODO:
1. Implement the fd_set with dynamic allocated fds.
2. Implement the epoll with select API.
3. Edit io.c to use the customized fd_set struct.

I'm trying to work on a branch for this. Any suggestions for this?

---Files--------------------------------
epoll.h (3.62 KB)
epoll.h (6.44 KB)


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