Principal Buffers

The principal buffer is present in every DTrace invocation and is the buffer to which tracing actions record their data by default. These actions include:

exit()	printf()	trace()	ustack()
printa()	stack()	tracemem()

The principal buffers are always allocated on a per-CPU basis. This policy is not tunable, but tracing and buffer allocation can be restricted to a single CPU by using the cpu option.