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Date: Mon, 30 Apr 2018 10:47:01 +0000
From: Eric Wong <normalperson@yhbt.net>
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Subject: [ruby-core:86775] Re: [Ruby trunk Feature#13618] [PATCH] auto fiber
 schedule for rb_wait_for_single_fd and rb_waitpid
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samuel@oriontransfer.org wrote:
> If you use any kind of thread-safe shared mutable state (e.g.
> a queue), you will invoke some kind of IPC (syscall) overhead.

There's unavoidable locking costs we're always paying inside
the kernel for every epoll_ctl/epoll_wait/kevent syscall.

> If you don't need to communicate between threads, you can
> avoid all IPC, e.g.
> https://github.com/socketry/async/blob/master/lib/async/queue.rb
> doesn't directly invoke any kind of IPC/syscall in order to
> function.

Since we're paying the locking cost inside the kernel,
we won't need to pay that cost in userspace (with one-shot).
So we might as well take advantage of the fact we're getting
"free" thread-safety from the kernel...