From: samuel@... Date: 2021-07-12T02:26:04+00:00 Subject: [ruby-core:104584] [Ruby master Bug#17664] Behavior of sockets changed in Ruby 3.0 to non-blocking Issue #17664 has been updated by ioquatix (Samuel Williams). I was playing around with a larger number of connections and the deferred submit: ``` io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 io_write:Event_Backend_fiber_transfer -> 46 select_process_completions(completed=38) ``` So certainly seems that it's capable of handling lots of events. But what I noticed is that there are a lot of minimally interleaved iterations: ``` io_write:Event_Backend_fiber_transfer -> 46 io_read:Event_Backend_fiber_transfer -> 40 select_process_completions(completed=2) io_write:Event_Backend_fiber_transfer -> 46 io_read:Event_Backend_fiber_transfer -> 40 select_process_completions(completed=2) io_write:Event_Backend_fiber_transfer -> 46 io_read:Event_Backend_fiber_transfer -> 40 select_process_completions(completed=2) io_write:Event_Backend_fiber_transfer -> 46 io_read:Event_Backend_fiber_transfer -> 40 select_process_completions(completed=2) ``` Maybe because `#accept` and `#close` are not asynchronous, it causes more issues. ---------------------------------------- Bug #17664: Behavior of sockets changed in Ruby 3.0 to non-blocking https://bugs.ruby-lang.org/issues/17664#change-92867 * Author: ciconia (Sharon Rosner) * Status: Assigned * Priority: Normal * Assignee: ioquatix (Samuel Williams) * ruby -v: 3.0.0 * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN ---------------------------------------- I'm not sure this is a bug, but apparently a change was introduced in Ruby 3.0 that makes sockets non-blocking by default. This change was apparently introduced as part of the work on the [FiberScheduler interface](https://github.com/ruby/ruby/blame/78f188524f551c97b1a7a44ae13514729f1a21c7/ext/socket/init.c#L411-L434). This change of behaviour is not discussed in the Ruby 3.0.0 release notes. This change complicates the implementation of an io_uring-based fiber scheduler, since io_uring SQE's on fd's with `O_NONBLOCK` can return `EAGAIN` just like normal syscalls. Using io_uring with non-blocking fd's defeats the whole purpose of using io_uring in the first place. A workaround I have put in place in the Polyphony [io_uring backend](https://github.com/digital-fabric/polyphony/blob/d3c9cf3ddc1f414387948fa40e5f6a24f68bf045/ext/polyphony/backend_io_uring.c#L28-L47) is to make sure `O_NONBLOCK` is not set before attempting I/O operations on any fd. -- https://bugs.ruby-lang.org/ Unsubscribe: