[PATCH 13/13] rbtree: optimize color flips in __rb_erase_color()

From: Michel Lespinasse
Date: Mon Jul 09 2012 - 19:36:23 EST


In __rb_erase_color(), when the current node is red or when flipping
the sibling's color, the parent is already known so we can use the
more efficient rb_set_parent_color() function to set the desired color.

Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
---
lib/rbtree.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/rbtree.c b/lib/rbtree.c
index c956248..f8c1a75 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -29,8 +29,6 @@
#define rb_color(r) ((r)->rb_parent_color & 1)
#define rb_is_red(r) (!rb_color(r))
#define rb_is_black(r) rb_color(r)
-#define rb_set_red(r) do { (r)->rb_parent_color &= ~1; } while (0)
-#define rb_set_black(r) do { (r)->rb_parent_color |= 1; } while (0)

static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
@@ -170,7 +168,7 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
* and tree rotations as per one of the 4 cases below.
*/
if (node && rb_is_red(node)) {
- rb_set_black(node);
+ rb_set_parent_color(node, parent, RB_BLACK);
break;
} else if (!parent) {
break;
@@ -190,7 +188,8 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
tmp2 = sibling->rb_left;
if (!tmp2 || rb_is_black(tmp2)) {
/* Case 2 - sibling color flip */
- rb_set_red(sibling);
+ rb_set_parent_color(sibling, parent,
+ RB_RED);
node = parent;
parent = rb_parent(node);
continue;
@@ -230,7 +229,8 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
tmp2 = sibling->rb_right;
if (!tmp2 || rb_is_black(tmp2)) {
/* Case 2 - sibling color flip */
- rb_set_red(sibling);
+ rb_set_parent_color(sibling, parent,
+ RB_RED);
node = parent;
parent = rb_parent(node);
continue;
--
1.7.7.3

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