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From: Maxime Devos <maximedevos@telenet.be>
To: Andrew Tropin <andrew@trop.in>, 49547@debbugs.gnu.org
Subject: [bug#49547] [PATCH v2 2/4] home-services: Add home-run-on-change-service-type
Date: Wed, 14 Jul 2021 12:41:35 +0200	[thread overview]
Message-ID: <ec097a03e2df002ef04a9ad80610ed3309a8dfce.camel@telenet.be> (raw)
In-Reply-To: <875yxem679.fsf@trop.in>

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Andrew Tropin schreef op ma 05-07-2021 om 18:39 [+0300]:
> +      (define (equal-regulars? file1 file2)
> +        "Check if FILE1 and FILE2 are bit for bit identical."
> +        (let* ((cmp-binary #$(file-append
> +                              (@ (gnu packages base) diffutils) "/bin/cmp"))
> +               (status (system* cmp-binary file1 file2)))
> +          (= status 0)))

Is there any particular reason to shell out to "cmp" instead
of doing the comparison in Guile?  Starting a process isn't
the most efficient thing.

Try "time /run/current-system/profile/bin echo", on my system,
it takes about 2--3 milliseconds for "echo" to finish
even though it only had to print a newline character.
Compare with "time echo" (to use the shell built-in "echo"),
it takes 0.000s seconds on my system.

3 milliseconds isn't much by itself, but this can accumulate,
so I would implement the comparison in Guile.

As an optimisation, you could look at the value returned by "lstat".
If the 'size' is different, then 'equal-regulars?' can return #f
without reading the file.  If the 'inode' and 'device' are equal,
then 'equal-regulars?' can return #t I think (at least on conventional
file systems like btrfs and ext4).

Greetings,
Maxime.

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  reply	other threads:[~2021-07-14 10:44 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-05 15:35 [bug#49419] [PATCH 0/4] Essential home services Andrew Tropin
2021-07-05 15:37 ` [bug#49419] [PATCH 1/4] home-services: Add most essential " Andrew Tropin
2021-07-05 15:47   ` Maxime Devos
2021-07-05 16:19     ` Andrew Tropin
2021-07-05 19:19       ` Maxime Devos
2021-07-06  7:09         ` Andrew Tropin
2021-07-06  8:26           ` Maxime Devos
2021-07-06  7:23     ` Andrew Tropin
2021-07-05 15:39 ` [bug#49419] [PATCH 2/4] home-services: Add home-run-on-change-service-type Andrew Tropin
2021-07-05 15:41 ` [bug#49419] [PATCH 3/4] home-services: Add home-provenance-service-type Andrew Tropin
2021-07-05 15:41 ` [bug#49419] [PATCH 4/4] home-services: Add fold-home-service-types function Andrew Tropin
2021-07-13 16:17 ` [bug#49419] [PATCH v2 0/4] Essential home services Andrew Tropin
2021-07-05 15:37   ` [bug#49546] [PATCH v2 1/4] home-services: Add most essential " Andrew Tropin
     [not found]     ` <handler.49546.B.16262002971832.ack@debbugs.gnu.org>
2021-07-13 18:24       ` [bug#49546] Acknowledgement ([PATCH v2 1/4] home-services: Add most essential home services) Andrew Tropin
2021-07-05 15:39   ` [bug#49547] [PATCH v2 2/4] home-services: Add home-run-on-change-service-type Andrew Tropin
2021-07-14 10:41     ` Maxime Devos [this message]
2021-07-15  8:46       ` Andrew Tropin
2021-07-18 16:17         ` Maxime Devos
2021-07-05 15:41   ` [bug#49548] [PATCH v2 3/4] home-services: Add home-provenance-service-type Andrew Tropin
2021-07-05 15:41   ` [bug#49549] [PATCH v2 4/4] home-services: Add fold-home-service-types function Andrew Tropin
2021-07-15  9:59   ` [bug#49568] Testing reply without debbugs address Andrew Tropin
2021-07-19  8:04 ` [bug#49419] [PATCH v3 0/4] Essential home services Andrew Tropin
2021-07-05 15:37   ` [bug#49419] [PATCH v3 1/4] home-services: Add most essential " Andrew Tropin
2021-07-05 15:39   ` [bug#49419] [PATCH v3 2/4] home-services: Add home-run-on-change-service-type Andrew Tropin
2021-07-05 15:41   ` [bug#49419] [PATCH v3 3/4] home-services: Add home-provenance-service-type Andrew Tropin
2021-07-05 15:41   ` [bug#49419] [PATCH v3 4/4] home-services: Add fold-home-service-types function Andrew Tropin
2021-07-21 15:08   ` [bug#49419] [PATCH 0/4] Essential home services Ludovic Courtès
2021-07-28  5:35     ` Andrew Tropin
     [not found] ` <handler.49419.B.162549932625345.ack@debbugs.gnu.org>
2021-08-05  5:41   ` [bug#49419] [PATCH v4 " Andrew Tropin
2021-08-05  5:45     ` [bug#49419] [PATCH v4 1/4] home-services: Add most essential " Andrew Tropin
2021-08-05  5:46     ` [bug#49419] [PATCH v4 2/4] home-services: Add home-run-on-change-service-type Andrew Tropin
2021-08-05  5:46     ` [bug#49419] [PATCH v4 3/4] home-services: Add home-provenance-service-type Andrew Tropin
2021-08-05  5:47     ` [bug#49419] [PATCH v4 4/4] home-services: Add fold-home-service-types function Andrew Tropin
2021-08-23  9:57     ` [bug#49419] [PATCH v4 0/4] Essential home services Andrew Tropin
2021-08-23 16:24       ` [bug#49419] [PATCH " Oleg Pykhalov
2021-08-24  8:53         ` Andrew Tropin
2021-08-24 12:14           ` bug#49419: " Oleg Pykhalov
2021-08-26  7:01             ` [bug#49419] " Andrew Tropin

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