Before this patch we can see very large time in the events before the
'bpf-output' event. For example:

  # perf trace -vv -T --ev sched:sched_switch \
                      --ev bpf-output/no-inherit,name=evt/ \
                      --ev ./test_bpf_trace.c/map:channel.event=evt/ \
                      usleep 10
  ...
  18446744073709.551 (18446564645918.480 ms): usleep/4157 nanosleep(rqtp: 0x7ffd3f0dc4e0) ...
  18446744073709.551 (         ): evt:Raise a BPF event!..)
  179427791.076 (         ): perf_bpf_probe:func_begin:(ffffffff810eb9a0))
  179427791.081 (         ): sched:sched_switch:usleep:4157 [120] S ==> swapper/2:0 [120])
  ...

We can also see the differences between bpf-output events and
breakpoint events:

For bpf output event:
   sample_type                    IP|TID|RAW|IDENTIFIER

For tracepoint events:
   sample_type                    IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER

This patch fix this differences by adding more sample type for
bpf-output events.

After this patch:

  # perf trace -vv -T --ev sched:sched_switch \
                      --ev bpf-output/no-inherit,name=evt/ \
                      --ev ./test_bpf_trace.c/map:channel.event=evt/ \
                      usleep 10
  ...
  179877370.878 ( 0.003 ms): usleep/5336 nanosleep(rqtp: 0x7ffff866c450) ...
  179877370.878 (         ): evt:Raise a BPF event!..)
  179877370.878 (         ): perf_bpf_probe:func_begin:(ffffffff810eb9a0))
  179877370.882 (         ): sched:sched_switch:usleep:5336 [120] S ==> swapper/4:0 [120])
  179877370.945 (         ): evt:Raise a BPF event!..)
  ...

  # ./perf trace -vv -T --ev sched:sched_switch \
                        --ev bpf-output/no-inherit,name=evt/ \
                        --ev ./test_bpf_trace.c/map:channel.event=evt/ \
                        usleep 10 2>&1 | grep sample_type
  sample_type                      IP|TID|TIME|ID|CPU|PERIOD|RAW
  sample_type                      IP|TID|TIME|ID|CPU|PERIOD|RAW
  sample_type                      IP|TID|TIME|ID|CPU|PERIOD|RAW
  sample_type                      IP|TID|TIME|ID|CPU|PERIOD|RAW
  sample_type                      IP|TID|TIME|ID|CPU|PERIOD|RAW
  sample_type                      IP|TID|TIME|ID|CPU|PERIOD|RAW

The 'IDENTIFIER' info is not required because all events have the same
sample_type.

Committer notes:

Further testing, on top of the changes making 'perf trace' avoid samples
from events without PERF_SAMPLE_TIME:

Before:

  # trace --ev bpf-output/no-inherit,name=evt/ --ev /home/acme/bpf/test_bpf_trace.c/map:channel.event=evt/ usleep 10
  <SNIP>
    0.560 ( 0.001 ms): brk(                                                   ) = 0x55e5a1df8000
    18446640227439.430 (18446640227438.859 ms): nanosleep(rqtp: 0x7ffc96643370) ...
    18446640227439.430 (         ): evt:Raise a BPF event!..)
    0.576 (         ): perf_bpf_probe:func_begin:(ffffffff81112460))
    18446640227439.430 (         ): evt:Raise a BPF event!..)
    0.645 (         ): perf_bpf_probe:func_end:(ffffffff81112460 <- ffffffff81003d92))
    0.646 ( 0.076 ms):  ... [continued]: nanosleep()) = 0
  #

After:

  # trace --ev bpf-output/no-inherit,name=evt/ --ev /home/acme/bpf/test_bpf_trace.c/map:channel.event=evt/ usleep 10
  <SNIP>
     0.292 ( 0.001 ms): brk(                          ) = 0x55c7cd6e1000
     0.302 ( 0.004 ms): nanosleep(rqtp: 0x7ffedd8bc0f0) ...
     0.302 (         ): evt:Raise a BPF event!..)
     0.303 (         ): perf_bpf_probe:func_begin:(ffffffff81112460))
     0.397 (         ): evt:Raise a BPF event!..)
     0.397 (         ): perf_bpf_probe:func_end:(ffffffff81112460 <- ffffffff81003d92))
     0.398 ( 0.100 ms):  ... [continued]: nanosleep()) = 0
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reported-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1459517202-42320-1-git-send-email-wangnan0@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>