From: Michel Lespinasse <walken@google.com>
To: aarcange@redhat.com, dwmw2@infradead.org, riel@redhat.com,
peterz@infradead.org, daniel.santos@pobox.com, axboe@kernel.dk,
ebiederm@xmission.com, akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org
Subject: [PATCH v2 10/12] rbtree: optimize case selection logic in __rb_erase_color()
Date: Thu, 12 Jul 2012 17:31:55 -0700 [thread overview]
Message-ID: <1342139517-3451-11-git-send-email-walken@google.com> (raw)
In-Reply-To: <1342139517-3451-1-git-send-email-walken@google.com>
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>
---
lib/rbtree.c | 68 +++++++++++++++++++++++++--------------------------------
1 files changed, 30 insertions(+), 38 deletions(-)
diff --git a/lib/rbtree.c b/lib/rbtree.c
index baf7c83..eb823a3 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;
}
}
}
--
1.7.7.3
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next prev parent reply other threads:[~2012-07-13 0:33 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-13 0:31 [PATCH v2 00/12] rbtree updates Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 01/12] rbtree: reference Documentation/rbtree.txt for usage instructions Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 02/12] rbtree: empty nodes have no color Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 03/12] rbtree: fix incorrect rbtree node insertion in fs/proc/proc_sysctl.c Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 04/12] rbtree: move some implementation details from rbtree.h to rbtree.c Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 05/12] rbtree: performance and correctness test Michel Lespinasse
2012-07-13 20:15 ` Andrew Morton
2012-07-13 22:33 ` Michel Lespinasse
2012-07-13 22:45 ` Andrew Morton
2012-07-13 23:09 ` Michel Lespinasse
2012-07-13 23:11 ` Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 06/12] rbtree: break out of rb_insert_color loop after tree rotation Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 07/12] rbtree: adjust root color in rb_insert_color() only when necessary Michel Lespinasse
2012-08-31 8:01 ` Adrian Hunter
2012-08-31 8:07 ` Michel Lespinasse
2012-08-31 8:15 ` Andrew Morton
2012-08-31 8:35 ` Adrian Hunter
2012-08-31 8:39 ` Michel Lespinasse
2012-09-06 20:47 ` Olof Johansson
2012-08-31 9:25 ` Alexander Shishkin
2012-09-08 1:26 ` Arnaldo Carvalho de Melo
2012-07-13 0:31 ` [PATCH v2 08/12] rbtree: low level optimizations in rb_insert_color() Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 09/12] rbtree: adjust node color in __rb_erase_color() only when necessary Michel Lespinasse
2012-07-13 0:31 ` Michel Lespinasse [this message]
2012-07-13 0:31 ` [PATCH v2 11/12] rbtree: low level optimizations in __rb_erase_color() Michel Lespinasse
2012-07-13 0:31 ` [PATCH v2 12/12] rbtree: coding style adjustments Michel Lespinasse
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