perf stat: Make --per-thread update shadow stats to show metrics

perf stat: Make --per-thread update shadow stats to show metrics

We should support this because it would allow easily to collect metrics
for different threads in applications.

Original patch from posted by Jin Yao in here [1].

1. Current output, for example:

root@skl:/tmp# perf stat --per-thread -p 21623
^C
 Performance counter stats for process id '21623':

          vmstat-21623              0.517479      task-clock (msec)         #    0.000 CPUs utilized
          vmstat-21623                     1      context-switches
          vmstat-21623                     0      cpu-migrations
          vmstat-21623                     0      page-faults
          vmstat-21623               461,306      cycles
          vmstat-21623               630,724      instructions
          vmstat-21623               136,265      branches
          vmstat-21623                 2,520      branch-misses

       1.444020756 seconds time elapsed

root@skl:/tmp# perf stat --per-thread --metrics ipc -p 21623
^C
 Performance counter stats for process id '21623':

          vmstat-21623               631,185      inst_retired.any
          vmstat-21623               605,893      cpu_clk_unhalted.thread

       1.415679293 seconds time elapsed

2. With this patch, the result would be:

root@skl:/tmp# perf stat --per-thread -p 21623
^C
 Performance counter stats for process id '21623':

          vmstat-21623              0.533759      task-clock (msec)         #    0.000 CPUs utilized
          vmstat-21623                     1      context-switches          #    0.002 M/sec
          vmstat-21623                     0      cpu-migrations            #    0.000 K/sec
          vmstat-21623                     0      page-faults               #    0.000 K/sec
          vmstat-21623               473,896      cycles                    #    0.888 GHz
          vmstat-21623               631,072      instructions              #    1.33  insn per cycle
          vmstat-21623               136,307      branches                  #  255.372 M/sec
          vmstat-21623                 2,524      branch-misses             #    1.85% of all branches

       1.544862861 seconds time elapsed

root@skl:/tmp# perf stat --per-thread --metrics ipc -p 21623
^C
 Performance counter stats for process id '21623':

          vmstat-21623             1,259,104      inst_retired.any          #      1.2 IPC
          vmstat-21623             1,056,756      cpu_clk_unhalted.thread

       2.040954502 seconds time elapsed

[1] https://marc.info/?l=linux-kernel&m=150777054620511&w=2

Originally-from: Jin Yao <yao.jin@linux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Changbin Du <changbin.du@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-tr8ntktxmy4qc5769ajg5u6c@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>