trace: apply node filter to root node too

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
trace: introduce --group-by option

This option will allow to introduce more grouping criterias than just
by thread. It replaces -m|--merge-threads option. Now by default there
is no grouping. Samples can be grouped by thread by passing '-g
thread'.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
trace: add ability to group profiles by CPU

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
trace: introduce --min-hits option

Useful in suppressing unimportant branches. Example:

Using percentage:

 trace.py --min-hits 10%

Using absolute count:

 trace.py --min-hits 3

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>