From: "Ludovic Courtès" <ludo@gnu.org>
To: "pelzflorian (Florian Pelz)" <pelzflorian@pelzflorian.de>
Cc: guix-devel@gnu.org
Subject: Re: The Shepherd on Fibers
Date: Tue, 29 Mar 2022 13:44:45 +0200 [thread overview]
Message-ID: <875ynx0yqa.fsf@gnu.org> (raw)
In-Reply-To: <20220326110627.dm3t7u2jtjxz5xf6@pelzflorian.localdomain> (pelzflorian@pelzflorian.de's message of "Sat, 26 Mar 2022 12:06:27 +0100")
Hi!
"pelzflorian (Florian Pelz)" <pelzflorian@pelzflorian.de> skribis:
> On Wed, Mar 23, 2022 at 11:36:30PM +0100, Ludovic Courtès wrote:
>> Fibers is used in a single-threaded fashion, which is the main
>> constraint for shepherd since it forks. That also means that fibers
>> cannot be preempted, so it’s fully cooperative scheduling.
>
> To understand what you mean, I needed to read shepherd commit
> 934204fbd158aa9fbd42914b89aa960f99eef125
>
> + ;; Run Fibers in such a way that it does not create any POSIX thread,
> + ;; because POSIX threads and 'fork' cannot be used together
>
> So shepherd service authors still cannot write blocking code but need
> to yield?
Yes. Technically though, “yielding” is transparent: any time you do I/O
(‘get-bytevector-n’, etc.) or call ‘sleep’ (specifically the one
provided by Fibers), your code potentially yields, letting Fibers
schedule some other activity.
What that means in practice is that starting services, waiting for PID
files, serving clients—all this happens concurrently.
It *is* possible to write service code that would block everything, but
with little or no effort, you can make it cooperate with the scheduler.
HTH,
Ludo’.
next prev parent reply other threads:[~2022-03-29 11:51 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 22:36 The Shepherd on Fibers Ludovic Courtès
2022-03-25 13:29 ` Maxim Cournoyer
2022-03-26 21:28 ` Ludovic Courtès
2022-03-26 11:06 ` pelzflorian (Florian Pelz)
2022-03-26 11:09 ` Zhu Zihao
2022-03-26 11:16 ` Zhu Zihao
2022-03-26 11:18 ` pelzflorian (Florian Pelz)
2022-03-26 11:27 ` Zhu Zihao
2022-03-26 16:56 ` pelzflorian (Florian Pelz)
2022-03-26 11:59 ` Maxime Devos
2022-03-26 16:52 ` pelzflorian (Florian Pelz)
2022-03-26 18:20 ` Maxime Devos
2022-03-29 11:44 ` Ludovic Courtès [this message]
2022-03-26 12:03 ` Maxime Devos
2022-03-29 12:47 ` Ludovic Courtès
2022-03-26 12:11 ` Maxime Devos
2022-03-29 12:48 ` Ludovic Courtès
2022-03-29 16:26 ` Maxime Devos
2022-03-30 15:14 ` Ludovic Courtès
2022-03-30 17:16 ` Maxime Devos
2022-03-26 12:16 ` Maxime Devos
2022-03-29 12:50 ` Ludovic Courtès
2022-03-29 12:52 ` Maxime Devos
2022-03-29 12:54 ` Maxime Devos
2022-03-29 15:29 ` Attila Lendvai
2022-03-30 10:05 ` Ludovic Courtès
2022-03-31 4:33 ` adriano
2022-03-31 7:56 ` Attila Lendvai
2022-03-26 12:44 ` Maxime Devos
2022-03-29 13:03 ` Ludovic Courtès
2022-03-26 19:24 ` Maxime Devos
2022-03-29 0:14 ` Philip McGrath
2022-03-29 0:22 ` Philip McGrath
2022-03-29 9:36 ` Maxime Devos
2022-03-29 11:11 ` Philip McGrath
2022-03-30 10:00 ` Ludovic Courtès
2022-03-29 10:13 ` Zhu Zihao
2022-03-29 10:40 ` Maxime Devos
2022-03-30 9:49 ` Ludovic Courtès
2022-03-29 13:16 ` Ludovic Courtès
-- strict thread matches above, loose matches on Subject: below --
2022-03-24 6:48 Brendan Tildesley
2022-03-24 16:57 Nathan Dehnel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://guix.gnu.org/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=875ynx0yqa.fsf@gnu.org \
--to=ludo@gnu.org \
--cc=guix-devel@gnu.org \
--cc=pelzflorian@pelzflorian.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/guix.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).