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From: Michel Lespinasse <walken@google.com>
To: riel@redhat.com, peterz@infradead.org, daniel.santos@pobox.com,
	aarcange@redhat.com, dwmw2@infradead.org,
	akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	torvalds@linux-foundation.org
Subject: [PATCH v3 3/9] rbtree: place easiest case first in rb_erase()
Date: Mon, 20 Aug 2012 15:05:25 -0700	[thread overview]
Message-ID: <1345500331-10546-4-git-send-email-walken@google.com> (raw)
In-Reply-To: <1345500331-10546-1-git-send-email-walken@google.com>

In rb_erase, move the easy case (node to erase has no more than
1 child) first. I feel the code reads easier that way.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>

---
 lib/rbtree.c |   35 ++++++++++++++++++-----------------
 1 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/lib/rbtree.c b/lib/rbtree.c
index de89a614b1ba..bde1b5c5fb33 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -368,17 +368,28 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
 {
-	struct rb_node *child, *parent;
+	struct rb_node *child = node->rb_right, *tmp = node->rb_left;
+	struct rb_node *parent;
 	int color;
 
-	if (!node->rb_left)
-		child = node->rb_right;
-	else if (!node->rb_right)
-		child = node->rb_left;
-	else {
+	if (!tmp) {
+	case1:
+		/* Case 1: node to erase has no more than 1 child (easy!) */
+
+		parent = rb_parent(node);
+		color = rb_color(node);
+
+		if (child)
+			rb_set_parent(child, parent);
+		__rb_change_child(node, child, parent, root);
+	} else if (!child) {
+		/* Still case 1, but this time the child is node->rb_left */
+		child = tmp;
+		goto case1;
+	} else {
 		struct rb_node *old = node, *left;
 
-		node = node->rb_right;
+		node = child;
 		while ((left = node->rb_left) != NULL)
 			node = left;
 
@@ -402,18 +413,8 @@ void rb_erase(struct rb_node *node, struct rb_root *root)
 		node->__rb_parent_color = old->__rb_parent_color;
 		node->rb_left = old->rb_left;
 		rb_set_parent(old->rb_left, node);
-
-		goto color;
 	}
 
-	parent = rb_parent(node);
-	color = rb_color(node);
-
-	if (child)
-		rb_set_parent(child, parent);
-	__rb_change_child(node, child, parent, root);
-
-color:
 	if (color == RB_BLACK)
 		__rb_erase_color(child, parent, root);
 }
-- 
1.7.7.3

WARNING: multiple messages have this Message-ID (diff)
From: Michel Lespinasse <walken@google.com>
To: riel@redhat.com, peterz@infradead.org, daniel.santos@pobox.com,
	aarcange@redhat.com, dwmw2@infradead.org,
	akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	torvalds@linux-foundation.org
Subject: [PATCH v3 3/9] rbtree: place easiest case first in rb_erase()
Date: Mon, 20 Aug 2012 15:05:25 -0700	[thread overview]
Message-ID: <1345500331-10546-4-git-send-email-walken@google.com> (raw)
In-Reply-To: <1345500331-10546-1-git-send-email-walken@google.com>

In rb_erase, move the easy case (node to erase has no more than
1 child) first. I feel the code reads easier that way.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>

---
 lib/rbtree.c |   35 ++++++++++++++++++-----------------
 1 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/lib/rbtree.c b/lib/rbtree.c
index de89a614b1ba..bde1b5c5fb33 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -368,17 +368,28 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
 {
-	struct rb_node *child, *parent;
+	struct rb_node *child = node->rb_right, *tmp = node->rb_left;
+	struct rb_node *parent;
 	int color;
 
-	if (!node->rb_left)
-		child = node->rb_right;
-	else if (!node->rb_right)
-		child = node->rb_left;
-	else {
+	if (!tmp) {
+	case1:
+		/* Case 1: node to erase has no more than 1 child (easy!) */
+
+		parent = rb_parent(node);
+		color = rb_color(node);
+
+		if (child)
+			rb_set_parent(child, parent);
+		__rb_change_child(node, child, parent, root);
+	} else if (!child) {
+		/* Still case 1, but this time the child is node->rb_left */
+		child = tmp;
+		goto case1;
+	} else {
 		struct rb_node *old = node, *left;
 
-		node = node->rb_right;
+		node = child;
 		while ((left = node->rb_left) != NULL)
 			node = left;
 
@@ -402,18 +413,8 @@ void rb_erase(struct rb_node *node, struct rb_root *root)
 		node->__rb_parent_color = old->__rb_parent_color;
 		node->rb_left = old->rb_left;
 		rb_set_parent(old->rb_left, node);
-
-		goto color;
 	}
 
-	parent = rb_parent(node);
-	color = rb_color(node);
-
-	if (child)
-		rb_set_parent(child, parent);
-	__rb_change_child(node, child, parent, root);
-
-color:
 	if (color == RB_BLACK)
 		__rb_erase_color(child, parent, root);
 }
-- 
1.7.7.3

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  parent reply	other threads:[~2012-08-20 22:07 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-20 22:05 [PATCH v3 0/9] faster augmented rbtree interface Michel Lespinasse
2012-08-20 22:05 ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 1/9] rbtree test: fix sparse warning about 64-bit constant Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 2/9] rbtree: add __rb_change_child() helper function Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:17   ` Andrew Morton
2012-08-20 22:17     ` Andrew Morton
2012-08-23 12:05     ` Jan Engelhardt
2012-08-23 12:05       ` Jan Engelhardt
2012-08-23 13:08       ` David Woodhouse
2012-09-26 22:34     ` Daniel Santos
2012-09-26 22:34       ` Daniel Santos
2012-09-26 22:43       ` Andrew Morton
2012-09-26 22:43         ` Andrew Morton
2012-08-20 22:05 ` Michel Lespinasse [this message]
2012-08-20 22:05   ` [PATCH v3 3/9] rbtree: place easiest case first in rb_erase() Michel Lespinasse
2012-08-20 22:28   ` Andrew Morton
2012-08-20 22:28     ` Andrew Morton
2012-08-20 22:05 ` [PATCH v3 4/9] rbtree: handle 1-child recoloring in rb_erase() instead of rb_erase_color() Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 5/9] rbtree: low level optimizations in rb_erase() Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 6/9] rbtree: augmented rbtree test Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 7/9] rbtree: faster augmented rbtree manipulation Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 8/9] rbtree: remove prior augmented rbtree implementation Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:05 ` [PATCH v3 9/9] rbtree: add RB_DECLARE_CALLBACKS() macro Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse

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