From: samuel@...
Date: 2018-06-12T03:57:57+00:00
Subject: [ruby-core:87477] [Ruby trunk Feature#14736] Thread selector for flexible cooperative fiber based concurrency

Issue #14736 has been updated by ioquatix (Samuel Williams).


I've been playing around with port scanners. Implemented in Go (goroutines), Python (asyncio) and Ruby (async).

I wrote up the results here: https://github.com/socketry/async-await/tree/master/examples/port_scanner

It was just an attempt to gauge the performance of the different implementations. It's by no means an authoritative comparison.

What I found interesting was that Ruby (async) was faster than Python (async) by about 2x. Go was faster again by about 2x. However, Go can use multiple CPU cores, and so because it utilised ~5 hardware threads, it was in effect about 10x faster.

I found that quite fascinating.

I don't believe we can easily adopt a model like goroutines in Ruby. However, it might be possible to adapt some of the good ideas from it.


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Feature #14736: Thread selector for flexible cooperative fiber based concurrency
https://bugs.ruby-lang.org/issues/14736#change-72473

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Ruby concurrency can be greatly enhanced by concurrent, deterministic IO.

Fibers have been shown many times to be a great abstraction for this purpose. The retain normal code flow and don't require any kind of Thread synchronisation. They are enjoyable to write code with because you don't have to concern yourself with thread synchronisation or other complicated issues.

The basic idea is that if some operation would block, it yields the Fiber, and other Fibers within the thread can continue to execute.

There are a number of ways to implement this. Here is a proof of concept to amend the existing `rb_io_wait_readable`/`rb_io_wait_writable`.

https://github.com/ruby/ruby/pull/1870

This design minimally affects the Ruby implementation and allows flexibility for selector implementation. With a small amount of work, we can support EventMachine (65 million downloads), NIO4r (21 million downloads). It would be trivial to back port.

This PR isn't complete but I am seeking feedback. If it's a good idea, I will do my best to see it through to completion, including support for EventMachine and NIO4r.



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