From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965799Ab2JaOtc (ORCPT ); Wed, 31 Oct 2012 10:49:32 -0400 Received: from casper.infradead.org ([85.118.1.10]:48020 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965759Ab2JaOtY (ORCPT ); Wed, 31 Oct 2012 10:49:24 -0400 From: Arnaldo Carvalho de Melo To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Andrew Vagin , Borislav Petkov , David Howells , Frederic Weisbecker , Jiri Olsa , Namhyung Kim , Paul Mackerras , Peter Zijlstra , Stephane Eranian , Steven Rostedt , Arnaldo Carvalho de Melo Subject: [PATCH 3/6] perf tools: Speed up the perf build time by simplifying the perf --version string generation Date: Wed, 31 Oct 2012 12:49:00 -0200 Message-Id: <1351694943-7188-4-git-send-email-acme@infradead.org> X-Mailer: git-send-email 1.7.9.2.358.g22243 In-Reply-To: <1351694943-7188-1-git-send-email-acme@infradead.org> References: <1351694943-7188-1-git-send-email-acme@infradead.org> Content-Type: text/plain; charset="utf-8" X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ingo Molnar Building perf is pretty slow on trees that have a lot of commits relative to the nearest Git tag. This slowness manifests itself during version string generation: $ perf stat --null --repeat 3 --sync --pre "rm -f PERF-VERSION-FILE" util/PERF-VERSION-GEN PERF_VERSION = 3.7.rc3.1458.g5399b3b PERF_VERSION = 3.7.rc3.1458.g5399b3b PERF_VERSION = 3.7.rc3.1458.g5399b3b Performance counter stats for 'util/PERF-VERSION-GEN' (3 runs): 2.857503976 seconds time elapsed ( +- 0.22% ) The build can be even slower than that, when one over NFS volumes. The reason for the slowness is that util/PERF-VERSION-GEN uses "git describe" to generate the string, which has to count the "number of commits distance" from the nearest tag - the ".1458." count in the output above. For that Git had to extract and decompress 1458 Git objects, which takes time and bandwidth. But this "number of commits" value is mostly irrelevant in practice. We either want to know an approximate tag name, or we want to know the precise sha1. So this patch simplifies the version string to: PERF_VERSION = 3.7.rc3.g5399b3b.dirty which speeds up the version string generation script by an order of magnitude: $ perf stat --null --repeat 3 --sync --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): 0.307633559 seconds time elapsed ( +- 0.84% ) Signed-off-by: Ingo Molnar Cc: Andrew Vagin Cc: Borislav Petkov Cc: David Howells Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Namhyung Kim Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20121030084600.GB8245@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/PERF-VERSION-GEN | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/util/PERF-VERSION-GEN b/tools/perf/util/PERF-VERSION-GEN index 95264f3..f6e8ee2 100755 --- a/tools/perf/util/PERF-VERSION-GEN +++ b/tools/perf/util/PERF-VERSION-GEN @@ -12,7 +12,7 @@ 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 if test -d ../../.git -o -f ../../.git && - VN=$(git describe --match 'v[0-9].[0-9]*' --abbrev=4 HEAD 2>/dev/null) && + VN=$(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]*) -- 1.7.9.2.358.g22243