ludo@HIDDEN (Ludovic Courtès)
to control <at> debbugs.gnu.org.
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From: ludo@HIDDEN (Ludovic =?utf-8?Q?Court=C3=A8s?=)
To: taylanbayirli@HIDDEN (Taylan Ulrich =?utf-8?Q?=22Bay=C4=B1rl=C4=B1?=
=?utf-8?Q?=2FKammer=22?=)
Subject: Re: bug#22608: Module system thread unsafety and .go compilation
In-Reply-To: <8737t1k5yk.fsf@HIDDEN> ("Taylan Ulrich
\=\?utf-8\?Q\?\=5C\=22Bay\=C4\=B1rl\=C4\=B1\=2FKammer\=5C\=22\=22's\?\=
message of "Tue, 09 Feb 2016 21:02:27 +0100")
References: <8737t1k5yk.fsf@HIDDEN>
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taylanbayirli@HIDDEN (Taylan Ulrich "Bay=C4=B1rl=C4=B1/Kammer") skribis:
> Sadly that assumption isn't met when autoloads are involved.
> Minimal-ish test-case:
>
> - Check out 0889321.
>
> - Build it.
>
> - Edit gnu/build/activation.scm and gnu/build/linux-boot.scm to contain
> merely the following expressions, respectively:
>
> (define-module (gnu build activation)
> #:use-module (gnu build linux-boot))
>
> (define-module (gnu build linux-boot)
> #:autoload (system base compile) (compile-file))
>
> - Run make again.
>
> If you're on a multi-core system, you will probably get an error saying
> something weird like "no such language scheme".
Do you have a clear explanation of why this happens? I would expect
(system base compile) to already be loaded for instance, so it=E2=80=99s not
clear to me what=E2=80=99s going on. Or is it just the mutation of (gnu bu=
ild
linux-boot) that=E2=80=99s causing problems?
> Solution proposals:
>
> 1. s/par-for-each/for-each/. Will make compilation slower on multi-core
> machines. We would do the same for guix pull, which is a bit sad
> because it's so fast right now. Very simple solution though.
>
> 2. We find out some partitioning of the Scheme modules such that there
> is minimal overlap in total loaded modules when the modules in one
> subset are each loaded by one Guile process. Then each Guile process
> loads & compiles the modules in its given subset serially, but these
> Guile processes run in parallel. This could speed things up even
> more than now because the module-loading phases of the processes
> would be parallel too. It also has the side-effect that less memory
> is consumed the fewer cores you have (because less Scheme modules
> loaded into memory at once). If someone (Ludo?) has a good general
> overview of Guix's module graph then maybe they can come up with a
> sensible partitioning of the modules, say into 4 subsets (maxing out
> benefits at quad-core), such that loading all modules in one subset
> loads a minimal amount of modules that are outside that subset. That
> should be the only challenging part of this solution.
>
> 3. We do nothing for now since this bug triggers rarely, and can be
> worked around by simply re-running make. (We just have to hope that
> it doesn't trigger on guix pull or on clean builds after some commit;
> there's no "just rerun make" in guix pull or an automated build of
> Guix.) AFAIU Wingo expressed motivation to make Guile's module
> system thread safe, so this problem would then truly disappear.
Short-term, I=E2=80=99d do #1 or #3; probably #1 though, because random fai=
lures
are no fun, and we know they can happen.
Longer-term, I=E2=80=99m not convinced by #2. I think I would instead build
packages in reverse topological order, probably serially at first, which
would address <http://bugs.gnu.org/15602> (with the caveat that the (gnu
packages =E2=80=A6) modules cannot be topologically-sorted, but OTOH they
typically don=E2=80=99t use macros, so we=E2=80=99re fine.)
That would require a tool to extract and the =E2=80=98define-module=E2=80=
=99 forms and
build a graph from there.
But really, we must fix <http://bugs.gnu.org/15602>, an in particular,
=E2=80=98compile-file=E2=80=99 should not mutate the global module name spa=
ce. I think
we could do something like:
(define (compile-file* =E2=80=A6)
(let ((root the-root-module)
(compile-root (copy-module the-root-module)))
(dynamic-wind
(lambda ()
(set! the-root-module compile-root)
;; ditto with the-scm-module
)
(lambda ()
(compile-file =E2=80=A6))
(lambda ()
(set! the-root-module root)
;; =E2=80=A6
))))
It=E2=80=99s unclear how costly =E2=80=98copy-module=E2=80=99 would be, and=
the whole strategy
depends on it.
Eventually it seems clear that Guile proper needs to address this use
case, and needs to provide thread-safe modules.
Ludo=E2=80=99.
bug-guix@HIDDEN:bug#22608; Package guix.
Full text available.
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From: ludo@HIDDEN (Ludovic =?utf-8?Q?Court=C3=A8s?=)
To: taylanbayirli@HIDDEN (Taylan Ulrich =?utf-8?Q?=22Bay=C4=B1rl=C4=B1?=
=?utf-8?Q?=2FKammer=22?=)
Subject: Re: bug#22608: Module system thread unsafety and .go compilation
References: <8737t1k5yk.fsf@HIDDEN>
Date: Wed, 10 Feb 2016 14:50:35 +0100
In-Reply-To: <8737t1k5yk.fsf@HIDDEN> ("Taylan Ulrich
\=\?utf-8\?Q\?\=5C\=22Bay\=C4\=B1rl\=C4\=B1\=2FKammer\=5C\=22\=22's\?\=
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taylanbayirli@HIDDEN (Taylan Ulrich "Bay=C4=B1rl=C4=B1/Kammer") skribis:
> Sadly that assumption isn't met when autoloads are involved.
> Minimal-ish test-case:
>
> - Check out 0889321.
>
> - Build it.
>
> - Edit gnu/build/activation.scm and gnu/build/linux-boot.scm to contain
> merely the following expressions, respectively:
>
> (define-module (gnu build activation)
> #:use-module (gnu build linux-boot))
>
> (define-module (gnu build linux-boot)
> #:autoload (system base compile) (compile-file))
>
> - Run make again.
>
> If you're on a multi-core system, you will probably get an error saying
> something weird like "no such language scheme".
Do you have a clear explanation of why this happens? I would expect
(system base compile) to already be loaded for instance, so it=E2=80=99s not
clear to me what=E2=80=99s going on. Or is it just the mutation of (gnu bu=
ild
linux-boot) that=E2=80=99s causing problems?
> Solution proposals:
>
> 1. s/par-for-each/for-each/. Will make compilation slower on multi-core
> machines. We would do the same for guix pull, which is a bit sad
> because it's so fast right now. Very simple solution though.
>
> 2. We find out some partitioning of the Scheme modules such that there
> is minimal overlap in total loaded modules when the modules in one
> subset are each loaded by one Guile process. Then each Guile process
> loads & compiles the modules in its given subset serially, but these
> Guile processes run in parallel. This could speed things up even
> more than now because the module-loading phases of the processes
> would be parallel too. It also has the side-effect that less memory
> is consumed the fewer cores you have (because less Scheme modules
> loaded into memory at once). If someone (Ludo?) has a good general
> overview of Guix's module graph then maybe they can come up with a
> sensible partitioning of the modules, say into 4 subsets (maxing out
> benefits at quad-core), such that loading all modules in one subset
> loads a minimal amount of modules that are outside that subset. That
> should be the only challenging part of this solution.
>
> 3. We do nothing for now since this bug triggers rarely, and can be
> worked around by simply re-running make. (We just have to hope that
> it doesn't trigger on guix pull or on clean builds after some commit;
> there's no "just rerun make" in guix pull or an automated build of
> Guix.) AFAIU Wingo expressed motivation to make Guile's module
> system thread safe, so this problem would then truly disappear.
Short-term, I=E2=80=99d do #1 or #3; probably #1 though, because random fai=
lures
are no fun, and we know they can happen.
Longer-term, I=E2=80=99m not convinced by #2. I think I would instead build
packages in reverse topological order, probably serially at first, which
would address <http://bugs.gnu.org/15602> (with the caveat that the (gnu
packages =E2=80=A6) modules cannot be topologically-sorted, but OTOH they
typically don=E2=80=99t use macros, so we=E2=80=99re fine.)
That would require a tool to extract and the =E2=80=98define-module=E2=80=
=99 forms and
build a graph from there.
But really, we must fix <http://bugs.gnu.org/15602>, an in particular,
=E2=80=98compile-file=E2=80=99 should not mutate the global module name spa=
ce. I think
we could do something like:
(define (compile-file* =E2=80=A6)
(let ((root the-root-module)
(compile-root (copy-module the-root-module)))
(dynamic-wind
(lambda ()
(set! the-root-module compile-root)
;; ditto with the-scm-module
)
(lambda ()
(compile-file =E2=80=A6))
(lambda ()
(set! the-root-module root)
;; =E2=80=A6
))))
It=E2=80=99s unclear how costly =E2=80=98copy-module=E2=80=99 would be, and=
the whole strategy
depends on it.
Eventually it seems clear that Guile proper needs to address this use
case, and needs to provide thread-safe modules.
Ludo=E2=80=99.
bug-guix@HIDDEN:bug#22608; Package guix.
Full text available.Received: (at submit) by debbugs.gnu.org; 9 Feb 2016 20:02:47 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Tue Feb 09 15:02:47 2016 Received: from localhost ([127.0.0.1]:33885 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1aTEUo-0004Tu-U6 for submit <at> debbugs.gnu.org; Tue, 09 Feb 2016 15:02:47 -0500 Received: from eggs.gnu.org ([208.118.235.92]:34697) by debbugs.gnu.org with esmtp (Exim 4.84) (envelope-from <taylanbayirli@HIDDEN>) id 1aTEUn-0004Ti-AF for submit <at> debbugs.gnu.org; Tue, 09 Feb 2016 15:02:45 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from <taylanbayirli@HIDDEN>) id 1aTEUd-00064n-76 for submit <at> debbugs.gnu.org; Tue, 09 Feb 2016 15:02:40 -0500 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on eggs.gnu.org X-Spam-Level: X-Spam-Status: No, score=0.8 required=5.0 tests=BAYES_50,FREEMAIL_FROM, T_DKIM_INVALID autolearn=disabled version=3.3.2 Received: from lists.gnu.org ([2001:4830:134:3::11]:56758) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from <taylanbayirli@HIDDEN>) id 1aTEUd-00064j-42 for submit <at> debbugs.gnu.org; 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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:user-agent :mime-version:content-type; bh=vahbhIvWVj41OaVJM9OS+1iR9q+B+w1Da14IMPLAj4s=; b=OM5p1VU1oYDlz8JzcCm9vh0xXGWPZz/JpianWuMQEfaJdSTqzRbYGOHnNrDacpgEuS s3m7BWyZ10E33pI/3lqXklFtfMQhEUmJKvjqMc18un2E9Sffn7+vagiBOw/Eb1ciSU09 VqmVGqAxxU1QnHyyOlWNg4eFbMQscQ39gvZIcddwUeryQksoWRGUrrp6SHFtvOX68kFf DAUzXJsMT6TCQTQ3Hq//bvDGIFVAEWJO+IWU55uhpHFBJMjslY0CMFuN61dwn065AO6r KrS1Ra5j/ZdlzPcpk8UybBpBhvzS1+1qTQC16ozS6Lg9wjhpRUfR2E09cogdXuLTc45G QJ5w== X-Gm-Message-State: AG10YOTNHBwF8CyJ4mBIIzKC1mYNNLlqmox6MXBxmgGzWZ5hUq8n+6MzLdriUC/Ij9AuPA== X-Received: by 10.28.103.5 with SMTP id b5mr7257922wmc.5.1455048149355; Tue, 09 Feb 2016 12:02:29 -0800 (PST) Received: from T420.taylan ([2a02:908:c30:3ec0:221:ccff:fe66:68f0]) by smtp.gmail.com with ESMTPSA id y188sm164723wmy.11.2016.02.09.12.02.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Feb 2016 12:02:28 -0800 (PST) From: taylanbayirli@HIDDEN (Taylan Ulrich =?utf-8?Q?Bay=C4=B1rl=C4=B1?= =?utf-8?Q?=2FKammer?=) To: bug-guix@HIDDEN Subject: Module system thread unsafety and .go compilation Date: Tue, 09 Feb 2016 21:02:27 +0100 Message-ID: <8737t1k5yk.fsf@HIDDEN> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 2001:4830:134:3::11 X-Spam-Score: -4.0 (----) X-Debbugs-Envelope-To: submit Cc: guile-devel@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -4.0 (----) To speed up the compilation of the many Scheme files in Guix, we use a script that first loads all modules to be compiled into the Guile process (by calling 'resolve-interface' on the module names), and then the corresponding Scheme files are compiled in a par-for-each. While Guile's module system is known to be thread unsafe, the idea was that all mutation should happen in the serial loading phase, and the parallel compile-file calls should then be thread safe. Sadly that assumption isn't met when autoloads are involved. Minimal-ish test-case: - Check out 0889321. - Build it. - Edit gnu/build/activation.scm and gnu/build/linux-boot.scm to contain merely the following expressions, respectively: (define-module (gnu build activation) #:use-module (gnu build linux-boot)) (define-module (gnu build linux-boot) #:autoload (system base compile) (compile-file)) - Run make again. If you're on a multi-core system, you will probably get an error saying something weird like "no such language scheme". Note: when you then run make *again* it succeeds. Solution proposals: 1. s/par-for-each/for-each/. Will make compilation slower on multi-core machines. We would do the same for guix pull, which is a bit sad because it's so fast right now. Very simple solution though. 2. We find out some partitioning of the Scheme modules such that there is minimal overlap in total loaded modules when the modules in one subset are each loaded by one Guile process. Then each Guile process loads & compiles the modules in its given subset serially, but these Guile processes run in parallel. This could speed things up even more than now because the module-loading phases of the processes would be parallel too. It also has the side-effect that less memory is consumed the fewer cores you have (because less Scheme modules loaded into memory at once). If someone (Ludo?) has a good general overview of Guix's module graph then maybe they can come up with a sensible partitioning of the modules, say into 4 subsets (maxing out benefits at quad-core), such that loading all modules in one subset loads a minimal amount of modules that are outside that subset. That should be the only challenging part of this solution. 3. We do nothing for now since this bug triggers rarely, and can be worked around by simply re-running make. (We just have to hope that it doesn't trigger on guix pull or on clean builds after some commit; there's no "just rerun make" in guix pull or an automated build of Guix.) AFAIU Wingo expressed motivation to make Guile's module system thread safe, so this problem would then truly disappear. I think #2 is a pretty good solution. The only thing worrying me is that we might not be able to sensibly partition the Scheme modules according to any simple logic that can be automated (like guix/ is one subset, gnu/packages/ is another, etc.). Maintaining the subsets manually in the Makefile would be pretty ugly. But maybe some simple logic, possibly combined with few special-cases in the code, would be good enough. Thoughts? Taylan
taylanbayirli@HIDDEN (Taylan Ulrich Bayırlı/Kammer):bug-guix@HIDDEN.
Full text available.bug-guix@HIDDEN:bug#22608; Package guix.
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