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Date: Wed, 31 Oct 2012 18:52:26 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <dsahern@gmail.com>, git@vger.kernel.org,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        linux-kernel@vger.kernel.org, Andrew Vagin <avagin@openvz.org>,
        Borislav Petkov <bp@amd64.org>, David Howells <dhowells@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>, Paul Mackerras <paulus@samba.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Stephane Eranian <eranian@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>, arnaldo.melo@gmail.com,
        Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: Re: 'git describe' is very slow on development trees with lots of
 commits
Message-ID: <20121031175226.GB20660@elf.ucw.cz>
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Hi!

> (Cc:-ed the Git development list.)
> 
> * David Ahern <dsahern@gmail.com> wrote:
> 
> > PERF-VERSION-GEN and specifically the git commands are the 
> > cause of more delay than the config checks, especially when 
> > doing the build in a VM with the kernel source on an NFS 
> > mount.
> 
> Yes, I have noticed that too.
....
> The cost on this pretty fast machine is about 1 msecs per commit 
> - which adds up to about 2.5 seconds during much of the 
> development cycle.

Well... I noticed my builds when little changed are very slow... and
it was due to the computation of version string. Ouch.

pavel@amd:~/mainline-altera/linux$ time git describe
fixes-for-linus-506-g71ca8691
0.68user 0.22system 27.82 (0m27.820s) elapsed 3.26%CPU
pavel@amd:~/mainline-altera/linux$ 

(Cached it is more reasonable 3 seconds, but it keeps going out of
cache all the time. Uncached clean build is 3 minutes, cached is 9
seconds + time to do git describe).

Thikpad X60.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html