tests: Note results of benchmarking of the gzip -1 flag on artifacts

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/lib b/tests/lib
index 883912c..2731f1e 100644
--- a/tests/lib
+++ b/tests/lib
@@ -507,6 +507,12 @@ t-save-artifacts () {
 	artifacts="$AUTOPKGTEST_ARTIFACTS"
 	if [ x"$artifacts" = x ]; then return; fi
 	if [ x"tmp" = x ]; then return; fi
+	# Empirically in a non-autopkgtest run with AUTOPKGTEST_ARTIFACTS
+	# this `-1` flag to gzip decreased the runtime from 585s (2558s CPU) 
+	# to 609s (2730s CPU), a decrease of 5-7%.  It increased the
+	# total size of the artifacts from 24220k to 26092k, ie +8%,
+	# but in a real autopkgtest run there are many bigger things
+	# alongside AUTOPKGTEST_ARTIFACTS put there by autopkgtest itself.
 	GZIP=-1v tar -C "$tmp" -zc -f "$artifacts/${0##*/}.tar.gz" \
 		--exclude=\*.tar .
 	local logfile="$DGIT_TEST_REDIRECTED_LOG"