Default Action

The default action applies when DTrace encounters an empty clause for a probe. The default action is to trace the enabled probe identifier (EPID).

The default action copies trace data from the EPID to the principal buffer. The following information is returned: CPU, probe ID, probe function, and probe name.

The default action provides the most direct use of the dtrace command. For example, running the following command enables all the probes in the vmlinux module with the default action:

sudo dtrace -m vmlinux

Output similar to the following is displayed:

dtrace: description 'vmlinux' matched 35 probes
CPU     ID                    FUNCTION:NAME
  0     42                 __schedule:sleep 
  0     34             dequeue_task:dequeue 
  0     40               __schedule:off-cpu 
  0     23        finish_task_switch:on-cpu 
  0     24             enqueue_task:enqueue 
  0     41               __schedule:preempt 
...