Re: kqueues and port_create()

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.lisp, comp.lang.c
Subject	Re: kqueues and port_create()
Date	2026-08-12 02:22 -0700
Organization	A noiseless patient Spider
Message-ID	<87y0ebpua6.fsf@nightsong.com> (permalink)
References	(16 earlier) <115do8s$3i42e$2@dont-email.me> <gAOeS.149915$jNNe.30359@fx15.ams4> <8733wkq995.fsf@nightsong.com> <LcTeS.214700$la89.26355@fx06.ams4> <864igzpzsu.fsf@williamsburg.bawden.org>

Cross-posted to 2 groups.

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Alan Bawden <alan@csail.mit.edu> writes:
> I _think_ what Paul was asking was is it possible to get notified when a
> specific file in the file system is opened.

No in linux that's called inotify.  io_uring is basically an alternative
system call interface that's relatively new, and maybe not complete.
You send off a request to do the system call, and get back a queued
response when the call is completed, unlike traditional syscalls that
appear to be synchronous.

One of the calls you can do that way is opening a file.  Historically in
Unix and Linux, there was no way to do that asynchronously.  If you used
open() and the operation was slow (for example NFS, or even anything on
a hard disk), your program would be blocked until the call returned.  If
you don't want to block, you have to do the open() in a separate thread.
GHC and Erlang BEAM have lightweight threads/processes, but they also
had a pool of OS threads to handle operations like opening files.

io_uring lets you open files asynchronously, so you can in principle
simulate an OS in a single user-level process.  More typically though,
io_uring is used as an alternative to something like epoll, for
listening on lots of sockets at the same time.  There are a lot of
benchmarks around that I think say io_uring is a little faster.
io_uring also can replace AIO, which never worked very well.  AIO was
for asynchronous disk i/o operations after the file was already open.

I haven't had occasion to use io_uring yet but I saw its importance when
it first appeared.

Thread

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            Re: Manipulating C code at the AST level, in C Paul Rubin <no.email@nospam.invalid> - 2026-08-10 01:11 -0700
              Re: Manipulating C code at the AST level, in C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-10 13:10 -0700
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                Re: Manipulating C code at the AST level, in C scott@slp53.sl.home (Scott Lurndal) - 2026-08-11 14:29 +0000
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                Re: kqueues and port_create() Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-12 13:07 +0800
                Re: kqueues and port_create() Alan Bawden <alan@csail.mit.edu> - 2026-08-12 03:23 -0400
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