perf tools: Store the cpu socket and core ids in the perf.data header

perf tools: Store the cpu socket and core ids in the perf.data header

This patch stores the cpu socket_id and core_id in a perf.data header,
and reads them into the perf_env struct when processing perf.data files.

The changes modifies the CPU_TOPOLOGY section, making sure it is
backward/forward compatible.

The patch checks the section size before reading the core and socket ids.

It never reads data crossing the section boundary.  An old perf binary
without this patch can also correctly read the perf.data from a new perf
with this patch.

Because the new info is added at the end of the cpu_topology section, an
old perf tool ignores the extra data.

Examples:

1. New perf with this patch read perf.data from an old perf without the
   patch:

  $ perf_new report -i perf_old.data --header-only -I
  ......
  # sibling threads : 33
  # sibling threads : 34
  # sibling threads : 35
  # Core ID and Socket ID information is not available
  # node0 meminfo  : total = 32823872 kB, free = 29315548 kB
  # node0 cpu list : 0-17,36-53
  ......

2. Old perf without the patch reads perf.data from a new perf with the
   patch:

  $ perf_old report -i perf_new.data --header-only -I
  ......
  # sibling threads : 33
  # sibling threads : 34
  # sibling threads : 35
  # node0 meminfo  : total = 32823872 kB, free = 29190932 kB
  # node0 cpu list : 0-17,36-53
  ......

3. New perf read new perf.data:

  $ perf_new report -i perf_new.data --header-only -I
  ......
  # sibling threads : 33
  # sibling threads : 34
  # sibling threads : 35
  # CPU 0: Core ID 0, Socket ID 0
  # CPU 1: Core ID 1, Socket ID 0
  ......
  # CPU 61: Core ID 10, Socket ID 1
  # CPU 62: Core ID 11, Socket ID 1
  # CPU 63: Core ID 16, Socket ID 1
  # node0 meminfo  : total = 32823872 kB, free = 29190932 kB
  # node0 cpu list : 0-17,36-53

Signed-off-by: Kan Liang <kan.liang@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/1441115893-22006-2-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>