+@end defopt
+
+@defopt gc-cons-percentage
+The value of this variable specifies the amount of consing before a
+garbage collection occurs, as a fraction of the current heap size.
+This criterion and @code{gc-cons-threshold} apply in parallel, and
+garbage collection occurs only when both criteria are satisfied.
+
+As the heap size increases, the time to perform a garbage collection
+increases. Thus, it can be desirable to do them less frequently in
+proportion.