GNU bug report logs - #67238
[PATCH] derivations: Avoid readlink syscalls in read-derivation-from-file.

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Message #8 received at 67238 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Christopher Baines <mail <at> cbaines.net>
Cc: Josselin Poiret <dev <at> jpoiret.xyz>, Tobias Geerinckx-Rice <me <at> tobias.gr>,
 Simon Tournier <zimon.toutoune <at> gmail.com>, Mathieu Othacehe <othacehe <at> gnu.org>,
 67238 <at> debbugs.gnu.org, Ricardo Wurmus <rekado <at> elephly.net>,
 Christopher Baines <guix <at> cbaines.net>
Subject: Re: [bug#67238] [PATCH] derivations: Avoid readlink syscalls in
 read-derivation-from-file.
Date: Fri, 24 Nov 2023 12:28:33 +0100

Hi,

Christopher Baines <mail <at> cbaines.net> skribis:

> strace -c reports over 10,000 readlink syscalls when reading the derivation
> for the hello package. By just setting the %file-port-name-canonicalization
> fluid, this drops to less than 10.
>
> I'm not sure if this actually improves performance, but doing less is surely
> better.
>
> * guix/derivations.scm (read-derivation-from-file): Set
> %file-port-name-canonicalization to 'none when calling call-with-input-file.
>
> Change-Id: I1ff16a059160576a576f2e9ed881379596e66af3

[...]

> +      (let ((drv
> +             ;; Avoid calling scm_i_relativize_path in
> +             ;; fport_canonicalize_filename since this leads to lots of
> +             ;; readlink calls
> +             (with-fluids ((%file-port-name-canonicalization 'none))
> +               (call-with-input-file file read-derivation))))

This is already done in ‘run-guix’ in (guix ui), for all the ‘guix’
commands (so this patch would be a slight performance regression for
Guix itself).

I’d suggest setting this fluid globally in applications that use Guix
(the Build Coordinator, etc.), as is done in Guix itself.

WDYT?

Ludo’.

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