perf sched timehist: Introduce timehist command

'perf sched timehist' provides an analysis of scheduling events.

Example usage:
    perf sched record -- sleep 1
    perf sched timehist

By default it shows the individual schedule events, including the wait
time (time between sched-out and next sched-in events for the task), the
task scheduling delay (time between wakeup and actually running) and run
time for the task:

            time    cpu  task name             wait time  sch delay   run time
                         [tid/pid]                (msec)     (msec)     (msec)
  -------------- ------  --------------------  ---------  ---------  ---------
    79371.874569 [0011]  gcc[31949]                0.014      0.000      1.148
    79371.874591 [0010]  gcc[31951]                0.000      0.000      0.024
    79371.874603 [0010]  migration/10[59]          3.350      0.004      0.011
    79371.874604 [0011]  <idle>                    1.148      0.000      0.035
    79371.874723 [0005]  <idle>                    0.016      0.000      1.383
    79371.874746 [0005]  gcc[31949]                0.153      0.078      0.022
...

Times are in msec.usec.

Committer note:

Add above explanation as the 'perf sched timehist' entry for 'man
perf-sched'.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20161116060634.28477-4-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-sched.txt

@@ -8,11 +8,11 @@ perf-sched - Tool to trace/measure scheduler properties (latencies)
 SYNOPSIS
 --------
 [verse]
-'perf sched' {record|latency|map|replay|script}
+'perf sched' {record|latency|map|replay|script|timehist}
 
 DESCRIPTION
 -----------
-There are five variants of perf sched:
+There are several variants of 'perf sched':
 
   'perf sched record <command>' to record the scheduling events
   of an arbitrary workload.
@@ -36,6 +36,30 @@ There are five variants of perf sched:
   are running on a CPU. A '*' denotes the CPU that had the event, and
   a dot signals an idle CPU.
 
+  'perf sched timehist' provides an analysis of scheduling events.
+    
+    Example usage:
+        perf sched record -- sleep 1
+        perf sched timehist
+    
+   By default it shows the individual schedule events, including the wait
+   time (time between sched-out and next sched-in events for the task), the
+   task scheduling delay (time between wakeup and actually running) and run
+   time for the task:
+    
+                time    cpu  task name             wait time  sch delay   run time
+                             [tid/pid]                (msec)     (msec)     (msec)
+      -------------- ------  --------------------  ---------  ---------  ---------
+        79371.874569 [0011]  gcc[31949]                0.014      0.000      1.148
+        79371.874591 [0010]  gcc[31951]                0.000      0.000      0.024
+        79371.874603 [0010]  migration/10[59]          3.350      0.004      0.011
+        79371.874604 [0011]  <idle>                    1.148      0.000      0.035
+        79371.874723 [0005]  <idle>                    0.016      0.000      1.383
+        79371.874746 [0005]  gcc[31949]                0.153      0.078      0.022
+    ...
+    
+   Times are in msec.usec.
+
 OPTIONS
 -------
 -i::
@@ -66,6 +90,28 @@ OPTIONS for 'perf sched map'
 --color-pids::
 	Highlight the given pids.
 
+OPTIONS for 'perf sched timehist'
+---------------------------------
+-k::
+--vmlinux=<file>::
+    vmlinux pathname
+
+--kallsyms=<file>::
+    kallsyms pathname
+
+-s::
+--summary::
+    Show only a summary of scheduling by thread with min, max, and average
+    run times (in sec) and relative stddev.
+
+-S::
+--with-summary::
+    Show all scheduling events followed by a summary by thread with min,
+    max, and average run times (in sec) and relative stddev.
+
+--symfs=<directory>::
+    Look for files with symbols relative to this directory.
+
 SEE ALSO
 --------
 linkperf:perf-record[1]