perf script: Add comm filtering option

Allows collecting events system wide and then pulling out events for a
specific task name(s). e.g,

    perf script -c gnome-shell,gnome-terminal

Applies on top of:
    https://lkml.org/lkml/2011/11/13/74

v2->v3
- update Documentation

v1->v2
- use comm_list from symbol_conf

Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: David Ahern <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
2 files changed