I found the parent symbol column data interesting even
if there's another sorting enabled. Switching it on.

Previous behaviour:
  $ perf report -i perf.data.delete -p perf_session__delete -x

  +   3.60%  perf  perf               [.] __rb_change_child
  +   1.89%  perf  perf               [.] rb_erase
  +   1.89%  perf  perf               [.] rb_erase
  +   1.83%  perf  perf               [.] free@plt

Current behaviour:
  $ perf report -i perf.data.delete -p perf_session__delete -x

  +   3.60%  perf  perf               [.] __rb_change_child        perf_session__delete
  +   1.89%  perf  perf               [.] rb_erase                 perf_session__delete_dead_threads
  +   1.89%  perf  perf               [.] rb_erase                 perf_session__delete_threads
  +   1.83%  perf  perf               [.] free@plt                 perf_session__delete
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-r79fn89bhqz16ixa5zmyflrd@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>