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

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Christopher Baines <mail <at> cbaines.net>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#67238: closed ([PATCH] derivations: Avoid readlink syscalls
 in read-derivation-from-file.)
Date: Sat, 25 Nov 2023 21:10:02 +0000

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Your message dated Sat, 25 Nov 2023 20:58:03 +0000
with message-id <87edgdmtew.fsf <at> cbaines.net>
and subject line Re: [bug#67238] [PATCH] derivations: Avoid readlink syscalls in read-derivation-from-file.
has caused the debbugs.gnu.org bug report #67238,
regarding [PATCH] derivations: Avoid readlink syscalls in read-derivation-from-file.
to be marked as done.

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67238: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67238
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From: Christopher Baines <mail <at> cbaines.net>
To: guix-patches <at> gnu.org
Subject: [PATCH] derivations: Avoid readlink syscalls in
 read-derivation-from-file.
Date: Fri, 17 Nov 2023 11:35:34 +0000

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
---
 guix/derivations.scm | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/guix/derivations.scm b/guix/derivations.scm
index 9fec7f4f0b..e6ecb570c4 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -556,7 +556,12 @@ (define (read-derivation-from-file file)
   ;; and because the same argument is read more than 15 times on average
   ;; during something like (package-derivation s gdb).
   (or (and file (hash-ref %derivation-cache file))
-      (let ((drv (call-with-input-file file read-derivation)))
+      (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))))
         (hash-set! %derivation-cache file drv)
         drv)))
 

base-commit: e35b7c5386c1bfacf47ed31bac9b503373dd26fc
-- 
2.41.0

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From: Christopher Baines <mail <at> cbaines.net>
To: Ludovic Courtès <ludo <at> gnu.org>
Cc: 67238-close <at> debbugs.gnu.org
Subject: Re: [bug#67238] [PATCH] derivations: Avoid readlink syscalls in
 read-derivation-from-file.
Date: Sat, 25 Nov 2023 20:58:03 +0000

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Ludovic Courtès <ludo <at> gnu.org> writes:

> 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?

Ah, I didn't realise it was already set for Guix scripts. But yeah,
setting it in other places that read derivations makes sense.

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