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authorLudovic Courtès <ludo@gnu.org>2021-03-14 15:05:30 +0100
committerLudovic Courtès <ludo@gnu.org>2021-03-21 23:41:01 +0100
commit9da5ec7099b992a8969a17627548cd341c01bd90 (patch)
tree82fa6307254029d42c3af67878c5f89dbdbc7164 /guix/narinfo.scm
parent5f9b28b231e17749d14a1b95ae9cad68d7315a1e (diff)
substitute: Choose compression method based on past CPU usage.
This stems from the observation that substitute download can be CPU-bound when high-speed networks are in use: https://lists.gnu.org/archive/html/guix-devel/2020-12/msg00177.html * guix/narinfo.scm (decompresses-faster?): New procedure. (narinfo-best-uri): Add #:fast-decompression?. * guix/scripts/substitute.scm (%prefer-fast-decompression?): New variable. (call-with-cpu-usage-monitoring): New procedure. (with-cpu-usage-monitoring): New macro. (display-narinfo-data, process-substitution): Pass #:fast-decompression? to 'narinfo-best-uri'. (process-substitution): Wrap 'restore-file' call in 'with-cpu-usage-monitoring'. Set '%prefer-fast-decompression?'.
Diffstat (limited to 'guix/narinfo.scm')
-rw-r--r--guix/narinfo.scm27
1 files changed, 23 insertions, 4 deletions
diff --git a/guix/narinfo.scm b/guix/narinfo.scm
index 2d06124017..72e0f75fda 100644
--- a/guix/narinfo.scm
+++ b/guix/narinfo.scm
@@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2014 Nikita Karetnikov <nikita@karetnikov.org>
;;; Copyright © 2018 Kyle Meyer <kyle@kyleam.com>
;;;
@@ -297,9 +297,21 @@ this is a rough approximation."
(_ (or (string=? compression2 "none")
(string=? compression2 "gzip")))))
-(define (narinfo-best-uri narinfo)
+(define (decompresses-faster? compression1 compression2)
+ "Return true if COMPRESSION1 generally has a higher decompression throughput
+than COMPRESSION2."
+ (match compression1
+ ("none" #t)
+ ("zstd" #t)
+ ("gzip" (string=? compression2 "lzip"))
+ (_ #f)))
+
+(define* (narinfo-best-uri narinfo #:key fast-decompression?)
"Select the \"best\" URI to download NARINFO's nar, and return three values:
-the URI, its compression method (a string), and the compressed file size."
+the URI, its compression method (a string), and the compressed file size.
+When FAST-DECOMPRESSION? is true, prefer substitutes with faster
+decompression (typically zstd) rather than substitutes with a higher
+compression ratio (typically lzip)."
(define choices
(filter (match-lambda
((uri compression file-size)
@@ -321,6 +333,13 @@ the URI, its compression method (a string), and the compressed file size."
(compresses-better? compression1 compression2))))
(_ #f))) ;we can't tell
- (match (sort choices file-size<?)
+ (define (speed<? c1 c2)
+ (match c1
+ ((uri1 compression1 . _)
+ (match c2
+ ((uri2 compression2 . _)
+ (decompresses-faster? compression2 compression1))))))
+
+ (match (sort choices (if fast-decompression? (negate speed<?) file-size<?))
(((uri compression file-size) _ ...)
(values uri compression file-size))))