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From: Andrew Morton <akpm@linux-foundation.org>
To: Michel Lespinasse <walken@google.com>
Cc: riel@redhat.com, peterz@infradead.org, daniel.santos@pobox.com,
	aarcange@redhat.com, dwmw2@infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, torvalds@linux-foundation.org
Subject: Re: [PATCH v3 3/9] rbtree: place easiest case first in rb_erase()
Date: Mon, 20 Aug 2012 15:28:02 -0700	[thread overview]
Message-ID: <20120820152802.272ec736.akpm@linux-foundation.org> (raw)
In-Reply-To: <1345500331-10546-4-git-send-email-walken@google.com>

On Mon, 20 Aug 2012 15:05:25 -0700
Michel Lespinasse <walken@google.com> wrote:

> 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.

Well.  For efficiency we should put the commonest case first.  Is that
the case here?

> --- 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;

Coding style nit: multiple-definitions-per-line makes it harder to
locate a particular definition, and from long experience I can assure
you that it makes management of subsequent overlapping patches quite a
lot harder.  Also, one-definition-per-line gives room for a nice little
comment, and we all like nice little comments.

Also, "tmp" is a rotten name.  Your choice of an identifier is your
opportunity to communicate something to the reader.  When you choose
"tmp", you threw away that opportunity.  Should it be called "left"?


--- a/lib/rbtree.c~rbtree-place-easiest-case-first-in-rb_erase-fix
+++ a/lib/rbtree.c
@@ -368,12 +368,13 @@ static void __rb_erase_color(struct rb_n
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
 {
-	struct rb_node *child = node->rb_right, *tmp = node->rb_left;
+	struct rb_node *child = node->rb_right
+	struct rb_node *tmp = node->rb_left;
 	struct rb_node *parent;
 	int color;
 
 	if (!tmp) {
-	case1:
+case1:
 		/* Case 1: node to erase has no more than 1 child (easy!) */
 
 		parent = rb_parent(node);
_


WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Michel Lespinasse <walken@google.com>
Cc: riel@redhat.com, peterz@infradead.org, daniel.santos@pobox.com,
	aarcange@redhat.com, dwmw2@infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, torvalds@linux-foundation.org
Subject: Re: [PATCH v3 3/9] rbtree: place easiest case first in rb_erase()
Date: Mon, 20 Aug 2012 15:28:02 -0700	[thread overview]
Message-ID: <20120820152802.272ec736.akpm@linux-foundation.org> (raw)
In-Reply-To: <1345500331-10546-4-git-send-email-walken@google.com>

On Mon, 20 Aug 2012 15:05:25 -0700
Michel Lespinasse <walken@google.com> wrote:

> 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.

Well.  For efficiency we should put the commonest case first.  Is that
the case here?

> --- 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;

Coding style nit: multiple-definitions-per-line makes it harder to
locate a particular definition, and from long experience I can assure
you that it makes management of subsequent overlapping patches quite a
lot harder.  Also, one-definition-per-line gives room for a nice little
comment, and we all like nice little comments.

Also, "tmp" is a rotten name.  Your choice of an identifier is your
opportunity to communicate something to the reader.  When you choose
"tmp", you threw away that opportunity.  Should it be called "left"?


--- a/lib/rbtree.c~rbtree-place-easiest-case-first-in-rb_erase-fix
+++ a/lib/rbtree.c
@@ -368,12 +368,13 @@ static void __rb_erase_color(struct rb_n
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
 {
-	struct rb_node *child = node->rb_right, *tmp = node->rb_left;
+	struct rb_node *child = node->rb_right
+	struct rb_node *tmp = node->rb_left;
 	struct rb_node *parent;
 	int color;
 
 	if (!tmp) {
-	case1:
+case1:
 		/* Case 1: node to erase has no more than 1 child (easy!) */
 
 		parent = rb_parent(node);
_

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  reply	other threads:[~2012-08-20 22:28 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 ` [PATCH v3 3/9] rbtree: place easiest case first in rb_erase() Michel Lespinasse
2012-08-20 22:05   ` Michel Lespinasse
2012-08-20 22:28   ` Andrew Morton [this message]
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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