These two functions can only be used by self-monitoring processes.
They have no effect on system wide sessions.
The pfm_self_start function activates monitoring. This function
is equivalent to calling perfmonctl() with the PFM_START
command and may end up calling it. On Linux/ia64 it is implemented
as a lightweight call to set the psr.up bit.
The pfm_self_stop function deactivates monitoring This function is
equivalent to calling perfmonctl() with the PFM_STOP command
and may end up calling it.On Linux/ia64 it is implemented as a lightweight
call to clear the psr.up bit.
RETURN
The function returns 0 if successful, otherwise -1 and the error code
is set in errno.