-@defvar gnus-registry-max-pruned-entries
-The maximum number (an integer or @code{nil} for unlimited) of entries
-the registry will keep after pruning.
+@defvar gnus-registry-prune-factor
+This option (a float between 0 and 1) controls how much the registry
+is cut back during pruning. In order to prevent constant pruning, the
+registry will be pruned back to less than
+@code{gnus-registry-max-entries}. This option controls exactly how
+much less: the target is calculated as the maximum number of entries
+minus the maximum number times this factor. The default is 0.1:
+i.e. if your registry is limited to 50000 entries, pruning will try to
+cut back to 45000 entries. Entries with keys marked as precious will
+not be pruned.
+@end defvar
+
+@defvar gnus-registry-default-sort-function
+This option specifies how registry entries are sorted during pruning.
+If a function is given, it should sort least valuable entries first,
+as pruning starts from the beginning of the list. The default value
+is @code{gnus-registry-sort-by-creation-time}, which proposes the
+oldest entries for pruning. Set to nil to perform no sorting, which
+will speed up the pruning process.