svn commit: r247771 - user/attilio/vmc-playground/sys/vm

[Alan Cox]

Author: alc
Date: Mon Mar  4 07:11:10 2013
New Revision: 247771
URL: http://svnweb.freebsd.org/changeset/base/247771

Log:
  Make a pass over most of the comments.

Modified:
  user/attilio/vmc-playground/sys/vm/vm_radix.c

Modified: user/attilio/vmc-playground/sys/vm/vm_radix.c
==============================================================================
--- user/attilio/vmc-playground/sys/vm/vm_radix.c	Mon Mar  4 06:26:25 2013	(r247770)
+++ user/attilio/vmc-playground/sys/vm/vm_radix.c	Mon Mar  4 07:11:10 2013	(r247771)
@@ -62,10 +62,9 @@
 #endif
 
 /*
- * Such sizes should permit to keep node children contained into a single
- * cache-line, or to at least not span many of those.
- * In particular, sparse tries should however be compressed properly and
- * then make some extra-levels not a big deal.
+ * These widths should allow the pointers to a node's children to fit within
+ * a single cache line.  The extra levels from a narrow width should not be
+ * a problem thanks to path compression.
  */
 #ifdef __LP64__
 #define	VM_RADIX_WIDTH	4
@@ -97,8 +96,8 @@ struct vm_radix_node {
 static uma_zone_t vm_radix_node_zone;
 
 /*
- * Allocate a radix node.  Pre-allocation ensures that the request will be
- * always successfully satisfied.
+ * Allocate a radix node.  Pre-allocation should ensure that the request
+ * will always be satisfied.
  */
 static __inline struct vm_radix_node *
 vm_radix_node_get(vm_pindex_t owner, uint16_t count, uint16_t clevel)
@@ -108,15 +107,15 @@ vm_radix_node_get(vm_pindex_t owner, uin
 	rnode = uma_zalloc(vm_radix_node_zone, M_NOWAIT | M_ZERO);
 
 	/*
-	 * The required number of nodes might be already correctly
-	 * pre-allocated in vm_radix_init().  However, UMA can reserve
-	 * few nodes on per-cpu specific buckets, which will not be
-	 * accessible from the curcpu.  The allocation could then
-	 * return NULL when the pre-allocation pool is close to be
-	 * exhausted.  Anyway, in practice this should never be a
-	 * problem because a new node is not always required for
-	 * insert, thus the pre-allocation pool should already have
-	 * some extra-pages that indirectly deal with this situation.
+	 * The required number of nodes should already be pre-allocated
+	 * by vm_radix_prealloc().  However, UMA can hold a few nodes
+	 * in per-CPU buckets, which will not be accessible by the
+	 * current CPU.  Thus, the allocation could return NULL when
+	 * the pre-allocated pool is close to exhaustion.  Anyway,
+	 * in practice this should never occur because a new node
+	 * is not always required for insert.  Thus, the pre-allocated
+	 * pool should have some extra pages that prevent this from
+	 * becoming a problem.
 	 */
 	if (rnode == NULL)
 		panic("%s: uma_zalloc() returned NULL for a new node",
@@ -184,7 +183,7 @@ vm_radix_setroot(struct vm_radix *rtree,
 
 /*
  * Returns the associated page extracted from rnode if available,
- * NULL otherwise.
+ * and NULL otherwise.
  */
 static __inline vm_page_t
 vm_radix_node_page(struct vm_radix_node *rnode)
@@ -195,7 +194,7 @@ vm_radix_node_page(struct vm_radix_node 
 }
 
 /*
- * Adds the page as a child of provided node.
+ * Adds the page as a child of the provided node.
  */
 static __inline void
 vm_radix_addpage(struct vm_radix_node *rnode, vm_pindex_t index, uint16_t clev,
@@ -229,7 +228,7 @@ vm_radix_keydiff(vm_pindex_t index1, vm_
 
 /*
  * Returns TRUE if it can be determined that key does not belong to the
- * specified rnode. FALSE otherwise.
+ * specified rnode.  Otherwise, returns FALSE.
  */
 static __inline boolean_t
 vm_radix_keybarr(struct vm_radix_node *rnode, vm_pindex_t idx)
@@ -296,7 +295,7 @@ vm_radix_declev(vm_pindex_t *idx, boolea
 }
 
 /*
- * Internal handwork for vm_radix_reclaim_allonodes() primitive.
+ * Internal helper for vm_radix_reclaim_allonodes().
  * This function is recursive.
  */
 static void
@@ -364,7 +363,7 @@ vm_radix_init(void)
 }
 
 /*
- * Inserts the key-value pair in to the trie.
+ * Inserts the key-value pair into the trie.
  * Panics if the key already exists.
  */
 void
@@ -452,7 +451,7 @@ vm_radix_insert(struct vm_radix *rtree, 
 }
 
 /*
- * Returns the value stored at the index.  If the index is not present
+ * Returns the value stored at the index.  If the index is not present,
  * NULL is returned.
  */
 vm_page_t
@@ -480,7 +479,7 @@ vm_radix_lookup(struct vm_radix *rtree, 
 }
 
 /*
- * Look up any entry at a position bigger than or equal to index.
+ * Look up the nearest entry at a position bigger than or equal to index.
  */
 vm_page_t
 vm_radix_lookup_ge(struct vm_radix *rtree, vm_pindex_t index)
@@ -553,7 +552,7 @@ restart:
 		}
 
 		/*
-		 * If a valid page or edge, bigger than the search slot, is
+		 * If a valid page or edge bigger than the search slot is
 		 * found in the traversal, skip to the next higher-level key.
 		 */
 		if (slot == (VM_RADIX_COUNT - 1) &&
@@ -569,7 +568,7 @@ restart:
 }
 
 /*
- * Look up any entry at a position less than or equal to index.
+ * Look up the nearest entry at a position less than or equal to index.
  */
 vm_page_t
 vm_radix_lookup_le(struct vm_radix *rtree, vm_pindex_t index)
@@ -643,7 +642,7 @@ restart:
 		}
 
 		/*
-		 * If a valid page or edge, smaller than the search slot, is
+		 * If a valid page or edge smaller than the search slot is
 		 * found in the traversal, skip to the next higher-level key.
 		 */
 		if (slot == 0 && (rnode->rn_child[slot] == NULL || m != NULL)) {
@@ -710,7 +709,7 @@ vm_radix_remove(struct vm_radix *rtree, 
 
 /*
  * Remove and free all the nodes from the radix tree.
- * This function is recrusive but there is a tight control on it as the
+ * This function is recursive but there is a tight control on it as the
  * maximum depth of the tree is fixed.
  */
 void