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authorMichel Lespinasse <walken@google.com>2012-10-08 16:31:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:35 +0900
commit59633abf34e2f44b8e772a2c12a92132aa7c2220 (patch)
tree3a260a6100ae2c3e2dbade989c3692234081f1c7 /lib
parent7ce6ff9e5de99e7b72019c7de82fb438fe1dc5a0 (diff)
downloadvexpress-lsk-59633abf34e2f44b8e772a2c12a92132aa7c2220.tar.gz
rbtree: optimize fetching of sibling node
When looking to fetch a node's sibling, we went through a sequence of: - check if node is the parent's left child - if it is, then fetch the parent's right child This can be replaced with: - fetch the parent's right child as an assumed sibling - check that node is NOT the fetched child This avoids fetching the parent's left child when node is actually that child. Saves a bit on code size, though it doesn't seem to make a large difference in speed. Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Woodhouse <David.Woodhouse@intel.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/rbtree.c21
1 files changed, 13 insertions, 8 deletions
diff --git a/lib/rbtree.c b/lib/rbtree.c
index 08926709b4f..61cdd0e3e53 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -107,8 +107,8 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
gparent = rb_red_parent(parent);
- if (parent == gparent->rb_left) {
- tmp = gparent->rb_right;
+ tmp = gparent->rb_right;
+ if (parent != tmp) { /* parent == gparent->rb_left */
if (tmp && rb_is_red(tmp)) {
/*
* Case 1 - color flips
@@ -131,7 +131,8 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
continue;
}
- if (parent->rb_right == node) {
+ tmp = parent->rb_right;
+ if (node == tmp) {
/*
* Case 2 - left rotate at parent
*
@@ -151,6 +152,7 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
RB_BLACK);
rb_set_parent_color(parent, node, RB_RED);
parent = node;
+ tmp = node->rb_right;
}
/*
@@ -162,7 +164,7 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
* / \
* n U
*/
- gparent->rb_left = tmp = parent->rb_right;
+ gparent->rb_left = tmp; /* == parent->rb_right */
parent->rb_right = gparent;
if (tmp)
rb_set_parent_color(tmp, gparent, RB_BLACK);
@@ -180,7 +182,8 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
continue;
}
- if (parent->rb_left == node) {
+ tmp = parent->rb_left;
+ if (node == tmp) {
/* Case 2 - right rotate at parent */
parent->rb_left = tmp = node->rb_right;
node->rb_right = parent;
@@ -189,10 +192,11 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
RB_BLACK);
rb_set_parent_color(parent, node, RB_RED);
parent = node;
+ tmp = node->rb_left;
}
/* Case 3 - left rotate at gparent */
- gparent->rb_right = tmp = parent->rb_left;
+ gparent->rb_right = tmp; /* == parent->rb_left */
parent->rb_left = gparent;
if (tmp)
rb_set_parent_color(tmp, gparent, RB_BLACK);
@@ -223,8 +227,9 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
break;
} else if (!parent) {
break;
- } else if (parent->rb_left == node) {
- sibling = parent->rb_right;
+ }
+ sibling = parent->rb_right;
+ if (node != sibling) { /* node == parent->rb_left */
if (rb_is_red(sibling)) {
/*
* Case 1 - left rotate at parent