Add 'perf stat record' command support. It creates simple (header only)
perf.data file ATM.

The record command could be specified anywhere among stat options. All
stat command options are valid for stat record command with '-o' option
exception. If specified for record command it denotes the perf data file
name.

Committer note:

Set sample_type to PERF_SAMPLE_IDENTIFIER, which should be harmless
while avoiding that older tools show confusing messages, for instance,
with sample_type = 0, we get:

  $ perf stat record usleep 1

   Performance counter stats for 'usleep 1':

          0.630237      task-clock (msec)         #    0.528 CPUs utilized
                 1      context-switches          #    0.002 M/sec
                 0      cpu-migrations            #    0.000 K/sec
                52      page-faults               #    0.083 M/sec
           978,312      cycles                    #    1.552 GHz
           671,931      stalled-cycles-frontend   #   68.68% frontend cycles idle
   <not supported>      stalled-cycles-backend
           646,379      instructions              #    0.66  insns per cycle
                                                  #    1.04  stalled cycles per insn
           131,046      branches                  #  207.931 M/sec
             7,073      branch-misses             #    5.40% of all branches

       0.001193240 seconds time elapsed

  $ oldperf evlist
  WARNING: The perf.data file's data size field is 0 which is unexpected.
  Was the 'perf record' command properly terminated?
  non matching sample_type
  $

While with sample_type set to PERF_SAMPLE_IDENTIFIER, after we re-run 'perf
stat record usleep' we get:

  $ oldperf evlist
  WARNING: The perf.data file's data size field is 0 which is unexpected.
  Was the 'perf record' command properly terminated?
  task-clock
  context-switches
  cpu-migrations
  page-faults
  cycles
  stalled-cycles-frontend
  stalled-cycles-backend
  instructions
  branches
  branch-misses
  $

Which at least shows the names of the events in the perf.data file.

Additionally, such files, when passed to 'perf report' will produce:

  $ oldperf report --stdio
  WARNING: The perf.data file's data size field is 0 which is unexpected.
  Was the 'perf record' command properly terminated?
  Warning:
  Kernel address maps (/proc/{kallsyms,modules}) were restricted.

  Check /proc/sys/kernel/kptr_restrict before running 'perf record'.

  As no suitable kallsyms nor vmlinux was found, kernel samples
  can't be resolved.

  Samples in kernel modules can't be resolved as well.

  Error:
  The perf.data file has no samples!
  # To display the perf.data header info, please use --header/--header-only options.
  #
  $

Which is confusing and can be solved by just adding the kernel mmap record,
which will also remove that warning about the data size field being equal to
zero, after generating the mmap record:

  $ perf stat record usleep 1

   Performance counter stats for 'usleep 1':

          0.600796      task-clock (msec)         #    0.478 CPUs utilized
                 1      context-switches          #    0.002 M/sec
                 0      cpu-migrations            #    0.000 K/sec
                54      page-faults               #    0.090 M/sec
           886,844      cycles                    #    1.476 GHz
           582,169      stalled-cycles-frontend   #   65.65% frontend cycles idle
   <not supported>      stalled-cycles-backend
           638,344      instructions              #    0.72  insns per cycle
                                                  #    0.91  stalled cycles per insn
           130,204      branches                  #  216.719 M/sec
             7,500      branch-misses             #    5.76% of all branches

       0.001255897 seconds time elapsed

  $ oldperf evlist
  task-clock
  context-switches
  cpu-migrations
  page-faults
  cycles
  stalled-cycles-frontend
  stalled-cycles-backend
  instructions
  branches
  branch-misses
  $ oldperf report --stdio
  Error:
  The perf.data file has no samples!
  # To display the perf.data header info, please use --header/--header-only options.
  #
  [acme@zoo linux]$

No warnings, sensible output about what are the events in the perf.data file and also
a "file has no samples" message, which indeed it doesn't.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Kan Liang <kan.liang@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: htp://lkml.kernel.org/r/1446734469-11352-3-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>