perf sched timehist: Add option to specify time window of interest

Add option to allow user to control analysis window. e.g., collect data
for time window and analyze a segment of interest within that window.

Committer notes:

Testing it:

  # perf sched record -a usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.593 MB perf.data (25 samples) ]
  #
  # perf sched timehist | head -18
  Samples do not have callchains.
          time    cpu   task name       wait time  sch delay  run time
                        [tid/pid]          (msec)     (msec)    (msec)
  ------------- ------  --------------- ---------  ---------  --------
   19818.635579 [0002]  <idle>              0.000      0.000     0.000
   19818.635613 [0000]  perf[9116]          0.000      0.000     0.000
   19818.635676 [0000]  <idle>              0.000      0.000     0.063
   19818.635678 [0000]  rcuos/2[29]         0.000      0.002     0.001
   19818.635696 [0002]  perf[9117]          0.000      0.004     0.116
   19818.635702 [0000]  <idle>              0.001      0.000     0.024
   19818.635709 [0002]  migration/2[25]     0.000      0.003     0.012
   19818.636263 [0000]  usleep[9117]        0.005      0.000     0.560
   19818.636316 [0000]  <idle>              0.560      0.000     0.053
   19818.636358 [0002]  <idle>              0.129      0.000     0.649
   19818.636358 [0000]  usleep[9117]        0.053      0.002     0.042
  #

  # perf sched timehist --time 19818.635696,
  Samples do not have callchains.
           time    cpu  task name       wait time  sch delay  run time
                        [tid/pid]          (msec)     (msec)    (msec)
  ------------- ------  ---------------  --------  --------- ---------
   19818.635696 [0002]  perf[9117]          0.000      0.120     0.000
   19818.635702 [0000]  <idle>              0.019      0.000     0.006
   19818.635709 [0002]  migration/2[25]     0.000      0.003     0.012
   19818.636263 [0000]  usleep[9117]        0.005      0.000     0.560
   19818.636316 [0000]  <idle>              0.560      0.000     0.053
   19818.636358 [0002]  <idle>              0.129      0.000     0.649
   19818.636358 [0000]  usleep[9117]        0.053      0.002     0.042
  #
  # perf sched timehist --time 19818.635696,19818.635709
  Samples do not have callchains.
           time    cpu  task name       wait time  sch delay  run time
                        [tid/pid]          (msec)     (msec)    (msec)
  ------------- ------  --------------- ---------  --------- ---------
   19818.635696 [0002]  perf[9117]          0.000      0.120     0.000
   19818.635702 [0000]  <idle>              0.019      0.000     0.006
   19818.635709 [0002]  migration/2[25]     0.000      0.003     0.012
   19818.635709 [0000]  usleep[9117]        0.005      0.000     0.006
  #

Signed-off-by: David Ahern <dsahern@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1480439746-42695-5-git-send-email-dsahern@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>