perf ftrace: Display latency statistics at the end

perf ftrace: Display latency statistics at the end

Sometimes users also want to see average latency as well as histogram.

Display latency statistics like avg, max, min at the end.

  $ sudo ./perf ftrace latency -ab -T synchronize_rcu -- ...
  #   DURATION     |      COUNT | GRAPH                                          |
       0 - 1    us |          0 |                                                |
       1 - 2    us |          0 |                                                |
       2 - 4    us |          0 |                                                |
       4 - 8    us |          0 |                                                |
       8 - 16   us |          0 |                                                |
      16 - 32   us |          0 |                                                |
      32 - 64   us |          0 |                                                |
      64 - 128  us |          0 |                                                |
     128 - 256  us |          0 |                                                |
     256 - 512  us |          0 |                                                |
     512 - 1024 us |          0 |                                                |
       1 - 2    ms |          0 |                                                |
       2 - 4    ms |          0 |                                                |
       4 - 8    ms |          0 |                                                |
       8 - 16   ms |          1 | #####                                          |
      16 - 32   ms |          7 | ########################################       |
      32 - 64   ms |          0 |                                                |
      64 - 128  ms |          0 |                                                |
     128 - 256  ms |          0 |                                                |
     256 - 512  ms |          0 |                                                |
     512 - 1024 ms |          0 |                                                |
       1 - ...   s |          0 |                                                |

  # statistics  (in usec)
    total time:               171832
      avg time:                21479
      max time:                30906
      min time:                15869
         count:                    8

Committer testing:

  root@number:~# perf ftrace latency -nab --bucket-range 100 --max-latency 512 -T switch_mm_irqs_off sleep 1
  #   DURATION     |      COUNT | GRAPH                                          |
       0 -  100 ns |        314 | ##                                             |
     100 -  200 ns |       1843 | #############                                  |
     200 -  300 ns |       1390 | ##########                                     |
     300 -  400 ns |        844 | ######                                         |
     400 -  500 ns |        480 | ###                                            |
     500 -  512 ns |        315 | ##                                             |
     512 -  ... ns |         16 |                                                |

  # statistics  (in nsec)
    total time:              2448936
      avg time:                  387
      max time:                 3285
      min time:                   82
         count:                 6328
  root@number:~#

Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250107224352.1128669-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>