(:total total :user user :system system)
where total, user and system are real numbers giving the total, user and system times in seconds spent inside the Garbage Collector while GC timing is on since the timing was last reset. When reset is non-nil,
get-gc-timing also switches GC timing off and resets the timing to 0. The default value of reset is
The GC timing is the same timing that is collected by extended-time. Once
start-gc-timing is called, extended-time does not try to collect GC timing and print it until
get-gc-timing is called with reset non-nil.
start-gc-timing (with initialize =
nil) can be used to collect GC timing only in specific periods without resetting the times. However the points at which the Garbage Collector is invoked are not well-defined, so the program may allocate while GC timing is on, and spend time Garbage Collecting after you stopped collecting.
LispWorks User Guide and Reference Manual - 20 Sep 2017