perf annotate browser: Show extra title line with event information

perf annotate browser: Show extra title line with event information

So at the top we'll have two lines, like this, from 'perf report':

  # perf report --group --ignore-vmlinux
=====================================================================================================
Samples: 46  of events 'cycles', 4000 Hz, Event count (approx.): 5154895
_raw_spin_lock_irqsave  /proc/kcore
Percent              │      nop
                     │      push   %rbx
  0.00  14.29   0.00 │      pushfq
  9.09   0.00   0.00 │      pop    %rax
  9.09   0.00  20.00 │      nop
                     │      mov    %rax,%rbx
                     │      cli
  4.55   7.14   0.00 │      nop
                     │      xor    %eax,%eax
                     │      mov    $0x1,%edx
                     │      lock   cmpxchg %edx,(%rdi)
 77.27  78.57  70.00 │      test   %eax,%eax
                     │    ↓ jne    2b
                     │      mov    %rbx,%rax
  0.00   0.00  10.00 │      pop    %rbx
                     │    ← retq
                     │2b:   mov    %eax,%esi
                     │    → callq  queued_spin_lock_slowpath
                     │      mov    %rbx,%rax
                     │      pop    %rbx
Press 'h' for help on│key bindings
=====================================================================================================

 9.09 + 9.09 + 4.55 + 77.27 = 100
14.29 + 7.14 + 78.57 = 100
20 + 70 + 10 = 100

We can do the math by using 't' to toggle from 'percent' to nr

=====================================================================================================
Samples: 46  of events 'cycles', 4000 Hz, Event count (approx.): 5154895
_raw_spin_lock_irqsave  /proc/kcore
Period                              │      nop
                                    │      push   %rbx
          0       79273           0 │      pushfq
     190455           0           0 │      pop    %rax
     198038           0        3045 │      nop
                                    │      mov    %rax,%rbx
                                    │      cli
     217233       32562           0 │      nop
                                    │      xor    %eax,%eax
                                    │      mov    $0x1,%edx
                                    │      lock   cmpxchg %edx,(%rdi)
    3421649      979174       28273 │      test   %eax,%eax
                                    │    ↓ jne    2b
                                    │      mov    %rbx,%rax
          0           0        5193 │      pop    %rbx
                                    │    ← retq
                                    │2b:   mov    %eax,%esi
                                    │    → callq  queued_spin_lock_slowpath
                                    │      mov    %rbx,%rax
                                    │      pop    %rbx
Press 'h' for help on│key bindings
=====================================================================================================

79273 + 190455 + 198038 + 3045 + 217233 + 32562 + 3421649 + 979174 + 28273 + 5193 = 5154895

Or number of samples:

=====================================================================================================
ooSamples: 46  of events 'cycles', 4000 Hz, Event count (approx.): 5154895
_raw_spin_lock_irqsave  /proc/kcore
Samples              │      nop
                     │      push   %rbx
     0      2      0 │      pushfq
     2      0      0 │      pop    %rax
     2      0      2 │      nop
                     │      mov    %rax,%rbx
                     │      cli
     1      1      0 │      nop
                     │      xor    %eax,%eax
                     │      mov    $0x1,%edx
                     │      lock   cmpxchg %edx,(%rdi)
    17     11      7 │      test   %eax,%eax
                     │    ↓ jne    2b
                     │      mov    %rbx,%rax
     0      0      1 │      pop    %rbx
                     │    ← retq
                     │2b:   mov    %eax,%esi
                     │    → callq  queued_spin_lock_slowpath
                     │      mov    %rbx,%rax
                     │      pop    %rbx
Press 'h' for help on key bindings
=====================================================================================================

2 + 2 + 2 + 2 + 1 + 1 + 17 + 11 + 7 + 1 = 46

Suggested-by: Martin Liška <mliska@suse.cz>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196935
Link: https://lkml.kernel.org/n/tip-ezccyxld50wtwyt66np6aomo@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>