There's another source of overhead in the perf version string
generator:
git update-index -q --refresh
... which will iterate the whole checked out tree. This can be
pretty slow on NFS volumes, but takes some time even with local
SSD disks and a fully cached kernel tree:
$ perf stat --null --repeat 3 --pre "rm -f PERF-VERSION-FILE"
util/PERF-VERSION-GEN
PERF_VERSION = 3.7.rc3.g5399b3b.dirty
PERF_VERSION = 3.7.rc3.g5399b3b.dirty
PERF_VERSION = 3.7.rc3.g5399b3b.dirty
Performance counter stats for 'util/PERF-VERSION-GEN' (3 runs):
0.306999221 seconds time elapsed
( +- 0.56% )
So remove the .dirty differentiator as well - it adds little
information because locally patched git trees are common, but
seldom are the perf tools modified.
So a lot of version strings are reported as 'dirty' while in
fact they are pristine perf builds. For example 99% of my perf
builds are not patched but the kernel tree is slightly patched,
which adds the .dirty tag.
Eliminating that tag speeds up version generation by another
order of magnitude:
$ perf stat --null --repeat 3 --sync --pre "rm -f PERF-VERSION-FILE"
util/PERF-VERSION-GEN
PERF_VERSION = 3.7.rc3.g4b0bd3
PERF_VERSION = 3.7.rc3.g4b0bd3
PERF_VERSION = 3.7.rc3.g4b0bd3
Performance counter stats for 'util/PERF-VERSION-GEN' (3 runs):
0.021270923 seconds time elapsed
( +- 1.94% )
(Also clean up some of the comments around this code.)
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
tools/perf/util/PERF-VERSION-GEN | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)
diff --git a/tools/perf/util/PERF-VERSION-GEN b/tools/perf/util/PERF-VERSION-GEN
index c774b89..6fb1cc8 100755
--- a/tools/perf/util/PERF-VERSION-GEN
+++ b/tools/perf/util/PERF-VERSION-GEN
@@ -9,17 +9,12 @@ GVF=${OUTPUT}PERF-VERSION-FILE
LF='
'
+#
# First check if there is a .git to get the version from git describe
-# otherwise try to get the version from the kernel makefile
+# otherwise try to get the version from the kernel Makefile
+#
if test -d ../../.git -o -f ../../.git &&
- VN=$(echo $(git tag --list "v[0-9].[0-9]*" | tail -1)"-g"$(git log -1
--abbrev=4 --pretty=format:"%h" HEAD) 2>/dev/null) &&
- case "$VN" in
- *$LF*) (exit 1) ;;
- v[0-9]*)
- git update-index -q --refresh
- test -z "$(git diff-index --name-only HEAD --)" ||
- VN="$VN-dirty" ;;
- esac
+ VN=$(echo $(git tag --list "v[0-9].[0-9]*" | tail -1)"-g"$(git log -1
--abbrev=4 --pretty=format:"%h" HEAD) 2>/dev/null)
then
VN=$(echo "$VN" | sed -e 's/-/./g');
else
--
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