From 78547a09e50440c649c3d28d7691f32fdd47cc25 Mon Sep 17 00:00:00 2001
From: Leo Famulari <address@hidden>
Date: Thu, 30 Mar 2017 03:10:48 -0400
Subject: [PATCH] packages: Enable threaded compression of source tarballs.

This provides a ~2x speedup when using 4 threads.

* guix/packages.scm (patch-and-repack)[build]: Invoke xz with
'--threads=0' when re-packing tarballs.
---
 guix/packages.scm | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/guix/packages.scm b/guix/packages.scm
index 4bc4b017f..30be5bf38 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -573,7 +573,12 @@ specifies modules in scope when evaluating SNIPPET."
                                                     #:fail-on-error? #t)))))
                         (zero? (apply system*
                                       (string-append #+tar "/bin/tar")
-                                      "cvfa" #$output
+                                      "cvf" #$output
+                                      ;; The bootstrap xz does not support
+                                      ;; threaded compression (introduced in
+                                      ;; 5.2.0), but it ignores the extra flag.
+                                      (string-append "--use-compress-program="
+                                                     #+xz "/bin/xz --threads=0")
                                       ;; avoid non-determinism in the archive
                                       "address@hidden"
                                       "--owner=root:0"
-- 
2.12.2