[PATCH 1/4] prio_tree: remove unnecessary code in prio_tree_replace

[PATCH 1/4] prio_tree: remove unnecessary code in prio_tree_replace

[Xiao Guangrong]

Remove the code since 'node' has already been initialized in the
begin of the function

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
 lib/prio_tree.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/lib/prio_tree.c b/lib/prio_tree.c
index ccfd850..423eba8 100644
--- a/lib/prio_tree.c
+++ b/lib/prio_tree.c
@@ -151,7 +151,6 @@ struct prio_tree_node *prio_tree_replace(struct prio_tree_root *root,
 		 * We can reduce root->index_bits here. However, it is complex
 		 * and does not help much to improve performance (IMO).
 		 */
-		node->parent = node;
 		root->prio_tree_node = node;
 	} else {
 		node->parent = old->parent;
-- 
1.7.7.6

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[PATCH 2/4] prio_tree: cleanup prio_tree_left/prio_tree_right

[Xiao Guangrong]

Introduce iter_walk_down/iter_walk_up to remove the common code
between prio_tree_left and prio_tree_right

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
 lib/prio_tree.c |   78 ++++++++++++++++++++++++++-----------------------------
 1 files changed, 37 insertions(+), 41 deletions(-)

diff --git a/lib/prio_tree.c b/lib/prio_tree.c
index 423eba8..888e8b3 100644
--- a/lib/prio_tree.c
+++ b/lib/prio_tree.c
@@ -304,6 +304,40 @@ void prio_tree_remove(struct prio_tree_root *root, struct prio_tree_node *node)
 		cur = prio_tree_replace(root, cur->parent, cur);
 }

+static void iter_walk_down(struct prio_tree_iter *iter)
+{
+	iter->mask >>= 1;
+	if (iter->mask) {
+		if (iter->size_level)
+			iter->size_level++;
+		return;
+	}
+
+	if (iter->size_level) {
+		BUG_ON(!prio_tree_left_empty(iter->cur));
+		BUG_ON(!prio_tree_right_empty(iter->cur));
+		iter->size_level++;
+		iter->mask = ULONG_MAX;
+	} else {
+		iter->size_level = 1;
+		iter->mask = 1UL << (BITS_PER_LONG - 1);
+	}
+}
+
+static void iter_walk_up(struct prio_tree_iter *iter)
+{
+	if (iter->mask == ULONG_MAX)
+		iter->mask = 1UL;
+	else if (iter->size_level == 1)
+		iter->mask = 1UL;
+	else
+		iter->mask <<= 1;
+	if (iter->size_level)
+		iter->size_level--;
+	if (!iter->size_level && (iter->value & iter->mask))
+		iter->value ^= iter->mask;
+}
+
 /*
  * Following functions help to enumerate all prio_tree_nodes in the tree that
  * overlap with the input interval X [radix_index, heap_index]. The enumeration
@@ -322,21 +356,7 @@ static struct prio_tree_node *prio_tree_left(struct prio_tree_iter *iter,

 	if (iter->r_index <= *h_index) {
 		iter->cur = iter->cur->left;
-		iter->mask >>= 1;
-		if (iter->mask) {
-			if (iter->size_level)
-				iter->size_level++;
-		} else {
-			if (iter->size_level) {
-				BUG_ON(!prio_tree_left_empty(iter->cur));
-				BUG_ON(!prio_tree_right_empty(iter->cur));
-				iter->size_level++;
-				iter->mask = ULONG_MAX;
-			} else {
-				iter->size_level = 1;
-				iter->mask = 1UL << (BITS_PER_LONG - 1);
-			}
-		}
+		iter_walk_down(iter);
 		return iter->cur;
 	}

@@ -363,22 +383,7 @@ static struct prio_tree_node *prio_tree_right(struct prio_tree_iter *iter,

 	if (iter->r_index <= *h_index) {
 		iter->cur = iter->cur->right;
-		iter->mask >>= 1;
-		iter->value = value;
-		if (iter->mask) {
-			if (iter->size_level)
-				iter->size_level++;
-		} else {
-			if (iter->size_level) {
-				BUG_ON(!prio_tree_left_empty(iter->cur));
-				BUG_ON(!prio_tree_right_empty(iter->cur));
-				iter->size_level++;
-				iter->mask = ULONG_MAX;
-			} else {
-				iter->size_level = 1;
-				iter->mask = 1UL << (BITS_PER_LONG - 1);
-			}
-		}
+		iter_walk_down(iter);
 		return iter->cur;
 	}

@@ -388,16 +393,7 @@ static struct prio_tree_node *prio_tree_right(struct prio_tree_iter *iter,
 static struct prio_tree_node *prio_tree_parent(struct prio_tree_iter *iter)
 {
 	iter->cur = iter->cur->parent;
-	if (iter->mask == ULONG_MAX)
-		iter->mask = 1UL;
-	else if (iter->size_level == 1)
-		iter->mask = 1UL;
-	else
-		iter->mask <<= 1;
-	if (iter->size_level)
-		iter->size_level--;
-	if (!iter->size_level && (iter->value & iter->mask))
-		iter->value ^= iter->mask;
+	iter_walk_up(iter);
 	return iter->cur;
 }

-- 
1.7.7.6

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[PATCH 3/4] prio_tree: simplify prio_tree_expand

[Xiao Guangrong]

In current code, the deleted-node is recorded from first to last,
actually, we can directly attach these node on 'node' we will insert
as the left child, it can let the code more readable

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
 lib/prio_tree.c |   38 ++++++++++++++------------------------
 1 files changed, 14 insertions(+), 24 deletions(-)

diff --git a/lib/prio_tree.c b/lib/prio_tree.c
index 888e8b3..928482b 100644
--- a/lib/prio_tree.c
+++ b/lib/prio_tree.c
@@ -94,43 +94,33 @@ static inline unsigned long prio_tree_maxindex(unsigned int bits)
 static struct prio_tree_node *prio_tree_expand(struct prio_tree_root *root,
 		struct prio_tree_node *node, unsigned long max_heap_index)
 {
-	struct prio_tree_node *first = NULL, *prev, *last = NULL;
+	struct prio_tree_node *prev;

 	if (max_heap_index > prio_tree_maxindex(root->index_bits))
 		root->index_bits++;

+	prev = node;
+	INIT_PRIO_TREE_NODE(node);
+
 	while (max_heap_index > prio_tree_maxindex(root->index_bits)) {
+		struct prio_tree_node *tmp = root->prio_tree_node;
+
 		root->index_bits++;

 		if (prio_tree_empty(root))
 			continue;

-		if (first == NULL) {
-			first = root->prio_tree_node;
-			prio_tree_remove(root, root->prio_tree_node);
-			INIT_PRIO_TREE_NODE(first);
-			last = first;
-		} else {
-			prev = last;
-			last = root->prio_tree_node;
-			prio_tree_remove(root, root->prio_tree_node);
-			INIT_PRIO_TREE_NODE(last);
-			prev->left = last;
-			last->parent = prev;
-		}
-	}
-
-	INIT_PRIO_TREE_NODE(node);
+		prio_tree_remove(root, root->prio_tree_node);
+		INIT_PRIO_TREE_NODE(tmp);

-	if (first) {
-		node->left = first;
-		first->parent = node;
-	} else
-		last = node;
+		prev->left = tmp;
+		tmp->parent = prev;
+		prev = tmp;
+	}

 	if (!prio_tree_empty(root)) {
-		last->left = root->prio_tree_node;
-		last->left->parent = last;
+		prev->left = root->prio_tree_node;
+		prev->left->parent = prev;
 	}

 	root->prio_tree_node = node;
-- 
1.7.7.6

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[PATCH 4/4] prio_tree: introduce prio_set_parent

[Xiao Guangrong]

Introduce prio_set_parent to abstraction the operation which
used to attach the node to its parent

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
 lib/prio_tree.c |   47 ++++++++++++++++++++++-------------------------
 1 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/lib/prio_tree.c b/lib/prio_tree.c
index 928482b..8d443af 100644
--- a/lib/prio_tree.c
+++ b/lib/prio_tree.c
@@ -85,6 +85,17 @@ static inline unsigned long prio_tree_maxindex(unsigned int bits)
 	return index_bits_to_maxindex[bits - 1];
 }

+static void prio_set_parent(struct prio_tree_node *parent,
+			    struct prio_tree_node *child, bool left)
+{
+	if (left)
+		parent->left = child;
+	else
+		parent->right = child;
+
+	child->parent = parent;
+}
+
 /*
  * Extend a priority search tree so that it can store a node with heap_index
  * max_heap_index. In the worst case, this algorithm takes O((log n)^2).
@@ -113,15 +124,12 @@ static struct prio_tree_node *prio_tree_expand(struct prio_tree_root *root,
 		prio_tree_remove(root, root->prio_tree_node);
 		INIT_PRIO_TREE_NODE(tmp);

-		prev->left = tmp;
-		tmp->parent = prev;
+		prio_set_parent(prev, tmp, true);
 		prev = tmp;
 	}

-	if (!prio_tree_empty(root)) {
-		prev->left = root->prio_tree_node;
-		prev->left->parent = prev;
-	}
+	if (!prio_tree_empty(root))
+		prio_set_parent(prev, root->prio_tree_node, true);

 	root->prio_tree_node = node;
 	return node;
@@ -142,23 +150,14 @@ struct prio_tree_node *prio_tree_replace(struct prio_tree_root *root,
 		 * and does not help much to improve performance (IMO).
 		 */
 		root->prio_tree_node = node;
-	} else {
-		node->parent = old->parent;
-		if (old->parent->left == old)
-			old->parent->left = node;
-		else
-			old->parent->right = node;
-	}
+	} else
+		prio_set_parent(old->parent, node, old->parent->left == old);

-	if (!prio_tree_left_empty(old)) {
-		node->left = old->left;
-		old->left->parent = node;
-	}
+	if (!prio_tree_left_empty(old))
+		prio_set_parent(node, old->left, true);

-	if (!prio_tree_right_empty(old)) {
-		node->right = old->right;
-		old->right->parent = node;
-	}
+	if (!prio_tree_right_empty(old))
+		prio_set_parent(node, old->right, false);

 	return old;
 }
@@ -218,16 +217,14 @@ struct prio_tree_node *prio_tree_insert(struct prio_tree_root *root,
 		if (index & mask) {
 			if (prio_tree_right_empty(cur)) {
 				INIT_PRIO_TREE_NODE(node);
-				cur->right = node;
-				node->parent = cur;
+				prio_set_parent(cur, node, false);
 				return res;
 			} else
 				cur = cur->right;
 		} else {
 			if (prio_tree_left_empty(cur)) {
 				INIT_PRIO_TREE_NODE(node);
-				cur->left = node;
-				node->parent = cur;
+				prio_set_parent(cur, node, true);
 				return res;
 			} else
 				cur = cur->left;
-- 
1.7.7.6

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Re: [PATCH 1/4] prio_tree: remove unnecessary code in prio_tree_replace

[Andrew Morton]

On Tue, 14 Feb 2012 16:59:49 +0800
Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> wrote:

> Remove the code since 'node' has already been initialized in the
> begin of the function
> 

The patches look good to me.

You appear to be the first person to touch this code in seven years. 
That must be a world record.

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