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authorMichel Lespinasse <walken@google.com>2012-10-08 16:30:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:34 +0900
commite125d1471a4f8f1bf7ea9a83deb8d23cb40bd712 (patch)
tree00c6bb561cdb8d0cb455563aa233bffe73b7e6db /lib
parentd6ff1273928ebf15466a85b7e1810cd00e72998b (diff)
downloadvexpress-lsk-e125d1471a4f8f1bf7ea9a83deb8d23cb40bd712.tar.gz
rbtree: optimize case selection logic in __rb_erase_color()
In __rb_erase_color(), we have to select one of 3 cases depending on the color on the 'other' node children. If both children are black, we flip a few node colors and iterate. Otherwise, we do either one or two tree rotations, depending on the color of the 'other' child opposite to 'node', and then we are done. The corresponding logic had duplicate checks for the color of the 'other' child opposite to 'node'. It was checking it first to determine if both children are black, and then to determine how many tree rotations are required. Rearrange the logic to avoid that extra check. Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: David Woodhouse <David.Woodhouse@intel.com> Cc: 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.c68
1 files changed, 30 insertions, 38 deletions
diff --git a/lib/rbtree.c b/lib/rbtree.c
index baf7c835c57..eb823a31099 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -283,28 +283,24 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
__rb_rotate_left(parent, root);
other = parent->rb_right;
}
- if ((!other->rb_left || rb_is_black(other->rb_left)) &&
- (!other->rb_right || rb_is_black(other->rb_right)))
- {
- rb_set_red(other);
- node = parent;
- parent = rb_parent(node);
- }
- else
- {
- if (!other->rb_right || rb_is_black(other->rb_right))
- {
- rb_set_black(other->rb_left);
+ if (!other->rb_right || rb_is_black(other->rb_right)) {
+ if (!other->rb_left ||
+ rb_is_black(other->rb_left)) {
rb_set_red(other);
- __rb_rotate_right(other, root);
- other = parent->rb_right;
+ node = parent;
+ parent = rb_parent(node);
+ continue;
}
- rb_set_color(other, rb_color(parent));
- rb_set_black(parent);
- rb_set_black(other->rb_right);
- __rb_rotate_left(parent, root);
- break;
+ rb_set_black(other->rb_left);
+ rb_set_red(other);
+ __rb_rotate_right(other, root);
+ other = parent->rb_right;
}
+ rb_set_color(other, rb_color(parent));
+ rb_set_black(parent);
+ rb_set_black(other->rb_right);
+ __rb_rotate_left(parent, root);
+ break;
} else {
other = parent->rb_left;
if (rb_is_red(other))
@@ -314,28 +310,24 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
__rb_rotate_right(parent, root);
other = parent->rb_left;
}
- if ((!other->rb_left || rb_is_black(other->rb_left)) &&
- (!other->rb_right || rb_is_black(other->rb_right)))
- {
- rb_set_red(other);
- node = parent;
- parent = rb_parent(node);
- }
- else
- {
- if (!other->rb_left || rb_is_black(other->rb_left))
- {
- rb_set_black(other->rb_right);
+ if (!other->rb_left || rb_is_black(other->rb_left)) {
+ if (!other->rb_right ||
+ rb_is_black(other->rb_right)) {
rb_set_red(other);
- __rb_rotate_left(other, root);
- other = parent->rb_left;
+ node = parent;
+ parent = rb_parent(node);
+ continue;
}
- rb_set_color(other, rb_color(parent));
- rb_set_black(parent);
- rb_set_black(other->rb_left);
- __rb_rotate_right(parent, root);
- break;
+ rb_set_black(other->rb_right);
+ rb_set_red(other);
+ __rb_rotate_left(other, root);
+ other = parent->rb_left;
}
+ rb_set_color(other, rb_color(parent));
+ rb_set_black(parent);
+ rb_set_black(other->rb_left);
+ __rb_rotate_right(parent, root);
+ break;
}
}
}