linux-kernel - [tip:perf/core] perf tools: Further speed up the perf build

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Date:	Tue, 13 Nov 2012 22:33:09 -0800
From:	tip-bot for Ingo Molnar <mingo@...nel.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, linux-kernel@...r.kernel.org, paulus@...ba.org,
	hpa@...or.com, mingo@...nel.org, a.p.zijlstra@...llo.nl,
	eranian@...il.com, namhyung@...nel.org, bp@...64.org,
	avagin@...nvz.org, jolsa@...hat.com, dhowells@...hat.com,
	fweisbec@...il.com, rostedt@...dmis.org, tglx@...utronix.de
Subject: [tip:perf/core] perf tools: Further speed up the perf build

Commit-ID:  0e2af956693a8797d658d076ff4c0da4147f0131
Gitweb:     http://git.kernel.org/tip/0e2af956693a8797d658d076ff4c0da4147f0131
Author:     Ingo Molnar <mingo@...nel.org>
AuthorDate: Tue, 30 Oct 2012 09:54:41 +0100
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Wed, 31 Oct 2012 12:17:49 -0200

perf tools: Further speed up the perf build

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 <mingo@...nel.org>
Cc: Andrew Vagin <avagin@...nvz.org>
Cc: Borislav Petkov <bp@...64.org>
Cc: David Howells <dhowells@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Stephane Eranian <eranian@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Link: http://lkml.kernel.org/r/20121030085441.GC8245@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/PERF-VERSION-GEN |   13 ++++---------
 1 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/PERF-VERSION-GEN b/tools/perf/util/PERF-VERSION-GEN
index f6e8ee2..ac418a1 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 $(git tag -l "v[0-9].[0-9]*" | tail -1)"-g"$(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 $(git tag -l "v[0-9].[0-9]*" | tail -1)"-g"$(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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