With the profiler running, the Lisp process is interrupted regularly at a specified time interval until the profiler is turned off. Having halted the execution of the process the profiler scans the execution stack and records information about it, including the names of all functions found. A special note is made of which function is at the top of the stack. After profiling stops the profiler can present a report containing a call tree and/or a cumulative columnar report.
The columnar report shows aggregated information about each function as follows:
The call tree shows name of a root function and a "tree" of callee functions below it. To the right of each function's name the number of times it was seen on the stack under a particular caller is shown, along with the percentage this represents of the total number of times the function was seen.
The call tree is more computationally expensive to record than the cumulative data. You can choose whether to record and output the call tree, as described in the next section.
LispWorks User Guide and Reference Manual - 21 Dec 2011