+/*
+ * FOOTPRINT ACCOUNTING:
+ * The "memory footprint" is better described in the pmap layer.
+ *
+ * At the VM level, these 2 vm_map_entry_t fields are relevant:
+ * iokit_mapped:
+ * For an "iokit_mapped" entry, we add the size of the entry to the
+ * footprint when the entry is entered into the map and we subtract that
+ * size when the entry is removed. No other accounting should take place.
+ * "use_pmap" should be FALSE but is not taken into account.
+ * use_pmap: (only when is_sub_map is FALSE)
+ * This indicates if we should ask the pmap layer to account for pages
+ * in this mapping. If FALSE, we expect that another form of accounting
+ * is being used (e.g. "iokit_mapped" or the explicit accounting of
+ * non-volatile purgable memory).
+ *
+ * So the logic is mostly:
+ * if entry->is_sub_map == TRUE
+ * anything in a submap does not count for the footprint
+ * else if entry->iokit_mapped == TRUE
+ * footprint includes the entire virtual size of this entry
+ * else if entry->use_pmap == FALSE
+ * tell pmap NOT to account for pages being pmap_enter()'d from this
+ * mapping (i.e. use "alternate accounting")
+ * else
+ * pmap will account for pages being pmap_enter()'d from this mapping
+ * as it sees fit (only if anonymous, etc...)
+ */
+