GNU bug report logs - #70494
[PATCH 00/23] Groundwork for the Guile guix-daemon

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From: Ludovic Courtès <ludo <at> gnu.org>
To: Christopher Baines <mail <at> cbaines.net>
Cc: Josselin Poiret <dev <at> jpoiret.xyz>, 70494 <at> debbugs.gnu.org, Simon Tournier <zimon.toutoune <at> gmail.com>, Mathieu Othacehe <othacehe <at> gnu.org>, Tobias Geerinckx-Rice <me <at> tobias.gr>, Ricardo Wurmus <rekado <at> elephly.net>, Christopher Baines <guix <at> cbaines.net>
Subject: [bug#70494] [PATCH 11/23] scripts: substitute: Untangle selecting fast vs small compressions.
Date: Thu, 16 May 2024 18:08:43 +0200

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

> Pulling the logic up to the script makes this code more portable and not
> reliant on setting a global variable.
>
> * guix/scripts/substitute.scm (%prefer-fast-decompression?): Rename to…
> (%default-prefer-fast-decompression?): this.
> (call-with-cpu-usage-monitoring): Use multiple values to return the results
> from the thunk as well as the cpu usage.
> (display-narinfo-data): Update accordingly.
> (download-nar): Add prefer-fast-decompression? as a keyword argument, remove
> code to set! it and monitor the cpu-usage.
> (process-substitution, process-substitution/fallback): Accept and pass through
> prefer-fast-decompression? to download-nar.
> (guix-substitute): Move the cpu usage monitoring and prefer fast decompression
> switching logic here.
>
> Change-Id: I4e80b457b55bcda8c0ff4ee224dd94a55e1b24fb

[...]

> +                 ;; Create a hysteresis: depending on CPU usage, favor
> +                 ;; compression methods with faster decompression (like ztsd)
> +                 ;; or methods with better compression ratios (like lzip).
> +                 ;; This stems from the observation that substitution can be
> +                 ;; CPU-bound when high-speed networks are used:
> +                 ;; <https://lists.gnu.org/archive/html/guix-devel/2020-12/msg00177.html>.
> +                 ;; To simulate "slow" networking or changing conditions, run:
> +                 ;; sudo tc qdisc add dev eno1 root tbf rate 512kbit latency
> +                 ;; 50ms burst 1540 and then cancel with: sudo tc qdisc del
> +                 ;; dev eno1 root

This comment’s formatting was broken (by M-q I guess).

Otherwise LGTM!

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