From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:470:142:3::10]:57378)
 by lists.gnu.org with esmtp (Exim 4.90_1)
 (envelope-from <Debian-debbugs@debbugs.gnu.org>) id 1ihDuJ-0006OC-GP
 for guix-patches@gnu.org; Tue, 17 Dec 2019 09:33:04 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
 (envelope-from <Debian-debbugs@debbugs.gnu.org>) id 1ihDuI-0007jQ-FT
 for guix-patches@gnu.org; Tue, 17 Dec 2019 09:33:03 -0500
Received: from debbugs.gnu.org ([209.51.188.43]:34917)
 by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16)
 (Exim 4.71) (envelope-from <Debian-debbugs@debbugs.gnu.org>)
 id 1ihDuI-0007ih-C9
 for guix-patches@gnu.org; Tue, 17 Dec 2019 09:33:02 -0500
Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2)
 (envelope-from <Debian-debbugs@debbugs.gnu.org>) id 1ihDuI-0004C5-8Y
 for guix-patches@gnu.org; Tue, 17 Dec 2019 09:33:02 -0500
Subject: [bug#38649] [PATCH] Parallelize `guix package`
Resent-Message-ID: <handler.38649.B38649.157659314516076@debbugs.gnu.org>
From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@gnu.org>
References: <c89e5b8436f2c53c9bb51a83a31eff0c9a71a1b5.camel@student.tugraz.at>
Date: Tue, 17 Dec 2019 15:32:10 +0100
In-Reply-To: <c89e5b8436f2c53c9bb51a83a31eff0c9a71a1b5.camel@student.tugraz.at>
 (Leo Prikler's message of "Tue, 17 Dec 2019 15:18:44 +0100")
Message-ID: <87tv5zrpjp.fsf@gnu.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
List-Id: <guix-patches.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/guix-patches>,
 <mailto:guix-patches-request@gnu.org?subject=unsubscribe>
List-Archive: <https://lists.gnu.org/archive/html/guix-patches>
List-Post: <mailto:guix-patches@gnu.org>
List-Help: <mailto:guix-patches-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/guix-patches>,
 <mailto:guix-patches-request@gnu.org?subject=subscribe>
Errors-To: guix-patches-bounces+kyle=kyleam.com@gnu.org
Sender: "Guix-patches" <guix-patches-bounces+kyle=kyleam.com@gnu.org>
To: Leo Prikler <leo.prikler@student.tugraz.at>
Cc: julien lepiller <roptat@lepiller.eu>, 38649@debbugs.gnu.org

Hi Leo,

(Cc: Julien, who worked on this part.)

Leo Prikler <leo.prikler@student.tugraz.at> skribis:

> Yesterday I had an interesting conversation on IRC about the behaviour
> of multiple `guix package` processes running in parallel.=20
> Specifically, when two transactions target the same profile (usually
> /var/guix/profiles/per-user/$USER/guix-profile) at the same time, one
> of them will fail to claim the lock and abort.  0001 makes it so that
> the process waits for the lock.  0002 makes it so that packages
> specified via -i can be built in parallel.

I actually like the current behavior, FWIW.  Julien came up with this
locking mostly so that people do not inadvertently attempt to perform
several operations concurrently.

The key word here is =E2=80=9Cinadvertently=E2=80=9D: IMO, there=E2=80=99s =
no reason to run
multiple =E2=80=98guix package=E2=80=99 on the same profile concurrently.  =
With a
wait-for-lock policy, the result would be non-deterministic: you cannot
tell which one of the two processes will complete first.

WDYT?

Thanks,
Ludo=E2=80=99.