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: NIngo Molnar <mingo@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Borislav Petkov <bp@amd64.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20121030085441.GC8245@gmail.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

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: NIngo Molnar <mingo@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Borislav Petkov <bp@amd64.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20121030084600.GB8245@gmail.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Before:

  $ perf --version
  perf version perf.urgent.for.mingo.5.g37da28

After:

  $ perf --version
  perf version 3.4.8941.g37da28.dirty

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-vc9b4e6023iegz9kabr3yvyv@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

When generating the perf version from the kernel version using 'make
kernelver' it is necessary to clear out any MAKEFLAGS otherwise they may
trigger additional output which pollute the contents.
Signed-off-by: NAndy Whitcroft <apw@canonical.com>
Signed-off-by: NMichal Marek <mmarek@suse.cz>

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: NMichal Marek <mmarek@suse.cz>

Some versions of grep don't treat '\s' properly. When building perf on such
systems and using a kernel tarball the perf version is unable to be determined
from the main kernel Makefile and the user is left with a version of '..'.
Replacing the use of '\s' with '[[:space:]]', which should work in all grep
versions, gives a usable version number.
Reported-by: NTapan Dhimant <tdhimant@akamai.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tapan Dhimant <tdhimant@akamai.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@kernel.org
LKML-Reference: <1300241800-30281-1-git-send-email-johunt@akamai.com>
Signed-off-by: NJosh Hunt <johunt@akamai.com>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

This gets rid of the default version fallback for Perf and
changes it so that it returns the version of the kernel from
it's Makefile (if sources were not from git, ie. if it was
downloaded from a tarball)
Signed-off-by: NThavidu Ranatunga <tharan@au1.ibm.com>
Acked-by: NIan Munsie <imunsie@au1.ibm.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1278316815-6099-2-git-send-email-tharan@au1.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Changes the Perf --version string such that it shows the kernel
version as suggested by Ingo as follows:

That way the perf that comes with v2.6.34 will be:

  perf version v2.6.34

while interim versions will have the version of the interim
kernel - for example:

 perf version v2.6.35-rc4-70-g39ef13a4

This functionality was already in the perf version generator
file except that it was looking for a .git in the perf directory
instead of the kernel directory.
Signed-off-by: NThavidu Ranatunga <tharan@au1.ibm.com>
Acked-by: NIan Munsie <imunsie@au1.ibm.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1278316815-6099-1-git-send-email-tharan@au1.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Avoiding polluting the source tree with build files.
Reported-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

We released the first version of perf with 0.0.1 in v2.6.31,
time to double our version number to 0.0.2 ;-)

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Several people have suggested that 'perf' has become a full-fledged
tool that should be moved out of Documentation/. Move it to the
(new) tools/ directory.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Clean up the top level directory a bit by moving all the helper libraries
to util/*.[ch].
Signed-off-by: NIngo Molnar <mingo@elte.hu>

First very raw version at having a central 'perf' command and
a list of subcommands:

  perf top
  perf stat
  perf record
  perf report
  ...

This is done by picking up Git's collection of utility functions,
and hacking them to build fine in this new environment.
Signed-off-by: NIngo Molnar <mingo@elte.hu>