perf_counter: some simple userspace profiling

perf_counter: some simple userspace profiling

# perf-record make -j4 kernel/
 # perf-report | tail -15

  0.39              cc1 [kernel] lock_acquired
  0.42              cc1 [kernel] lock_acquire
  0.51              cc1 [ user ] /lib64/libc-2.8.90.so: _int_free
  0.51               as [kernel] clear_page_c
  0.53              cc1 [ user ] /lib64/libc-2.8.90.so: memcpy
  0.56              cc1 [ user ] /lib64/libc-2.8.90.so: _IO_vfprintf
  0.63              cc1 [kernel] lock_release
  0.67              cc1 [ user ] /lib64/libc-2.8.90.so: strlen
  0.68              cc1 [kernel] debug_smp_processor_id
  1.38              cc1 [ user ] /lib64/libc-2.8.90.so: _int_malloc
  1.55              cc1 [ user ] /lib64/libc-2.8.90.so: memset
  1.77              cc1 [kernel] __lock_acquire
  1.88              cc1 [kernel] clear_page_c
  3.61               as [ user ] /usr/bin/as: <unknown>
 59.16              cc1 [ user ] /usr/libexec/gcc/x86_64-redhat-linux/4.3.2/cc1: <unknown>

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
LKML-Reference: <20090408130409.220518450@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>