Document VM.request-garbage-collection

doc/Type/VM.rakudoc

@@ -36,4 +36,18 @@ that should be used when precompiling source-files with the VM object.
 Instance method returning a string of the path in which the virtual machine
 of the VM object is installed.
 
+=head2 method request-garbage-collection
+
+Available as of the 2020.05 release of the Rakudo compiler.
+
+Class method that tells the virtual machine on which Raku is running, to
+perform a garbage collect run when possible.  Issues a warning if such a
+request is not supported by the virtual machine.
+
+Provides no guarantee that the process will actually use less memory after
+a garbage collect.  In fact, calling this method repeatedly, may actually
+cause more memory to be used due to memory fragmentation.
+
+Mainly intended as a debugging aid for module / core developers.
+
 =end pod