perf stat: Display user and system time

Adding the support to read rusage data once the workload is finished and
display the system/user time values:

  $ perf stat --null perf bench sched pipe
  ...

   Performance counter stats for 'perf bench sched pipe':

       5.342599256 seconds time elapsed

       2.544434000 seconds user
       4.549691000 seconds sys

It works only in non -r mode and only for workload target.

So as of now, for workload targets, we display 3 types of timings. The
time we meassure in perf stat from enable to disable+period:

       5.342599256 seconds time elapsed

The time spent in user and system lands, displayed only for workload
session/target:

       2.544434000 seconds user
       4.549691000 seconds sys

Those times are the very same displayed by 'time' tool.  They are
returned by wait4 call via the getrusage struct interface.

Committer notes:

Had to rename some variables to avoid this on older systems such as
centos:6:

  builtin-stat.c: In function 'print_footer':
  builtin-stat.c:1831: warning: declaration of 'stime' shadows a global declaration
  /usr/include/time.h:297: warning: shadowed declaration is here

Committer testing:

  # perf stat --null time perf bench sched pipe
  # Running 'sched/pipe' benchmark:
  # Executed 1000000 pipe operations between two processes

       Total time: 5.526 [sec]

         5.526534 usecs/op
           180945 ops/sec
  1.00user 6.25system 0:05.52elapsed 131%CPU (0avgtext+0avgdata 8056maxresident)k
  0inputs+0outputs (0major+606minor)pagefaults 0swaps

   Performance counter stats for 'time perf bench sched pipe':

         5.530978744 seconds time elapsed

         1.004037000 seconds user
         6.259937000 seconds sys

  #

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180605121313.31337-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 29 insertions, 11 deletions

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 3a822f308e6d..5dfe102fb5b5 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -310,20 +310,38 @@ Users who wants to get the actual value can apply --no-metric-only.
 EXAMPLES
 --------
 
-$ perf stat -- make -j
+$ perf stat -- make
 
- Performance counter stats for 'make -j':
+   Performance counter stats for 'make':
 
-    8117.370256  task clock ticks     #      11.281 CPU utilization factor
-            678  context switches     #       0.000 M/sec
-            133  CPU migrations       #       0.000 M/sec
-         235724  pagefaults           #       0.029 M/sec
-    24821162526  CPU cycles           #    3057.784 M/sec
-    18687303457  instructions         #    2302.138 M/sec
-      172158895  cache references     #      21.209 M/sec
-       27075259  cache misses         #       3.335 M/sec
+        83723.452481      task-clock:u (msec)       #    1.004 CPUs utilized
+                   0      context-switches:u        #    0.000 K/sec
+                   0      cpu-migrations:u          #    0.000 K/sec
+           3,228,188      page-faults:u             #    0.039 M/sec
+     229,570,665,834      cycles:u                  #    2.742 GHz
+     313,163,853,778      instructions:u            #    1.36  insn per cycle
+      69,704,684,856      branches:u                #  832.559 M/sec
+       2,078,861,393      branch-misses:u           #    2.98% of all branches
 
- Wall-clock time elapsed:   719.554352 msecs
+        83.409183620 seconds time elapsed
+
+        74.684747000 seconds user
+         8.739217000 seconds sys
+
+TIMINGS
+-------
+As displayed in the example above we can display 3 types of timings.
+We always display the time the counters were enabled/alive:
+
+        83.409183620 seconds time elapsed
+
+For workload sessions we also display time the workloads spent in
+user/system lands:
+
+        74.684747000 seconds user
+         8.739217000 seconds sys
+
+Those times are the very same as displayed by the 'time' tool.
 
 CSV FORMAT
 ----------