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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 2/9] rbtree: add __rb_change_child() helper function
Date: Mon, 20 Aug 2012 15:17:10 -0700	[thread overview]
Message-ID: <20120820151710.eeed9bcf.akpm@linux-foundation.org> (raw)
In-Reply-To: <1345500331-10546-3-git-send-email-walken@google.com>

On Mon, 20 Aug 2012 15:05:24 -0700
Michel Lespinasse <walken@google.com> wrote:

> Add __rb_change_child() as an inline helper function to replace code that
> would otherwise be duplicated 4 times in the source.
> 
> No changes to binary size or speed.
> 
> ...
>
> --- a/lib/rbtree.c
> +++ b/lib/rbtree.c
> @@ -66,6 +66,19 @@ static inline struct rb_node *rb_red_parent(struct rb_node *red)
>  	return (struct rb_node *)red->__rb_parent_color;
>  }
>  
> +static inline void
> +__rb_change_child(struct rb_node *old, struct rb_node *new,
> +		  struct rb_node *parent, struct rb_root *root)
> +{
> +	if (parent) {
> +		if (parent->rb_left == old)
> +			parent->rb_left = new;
> +		else
> +			parent->rb_right = new;
> +	} else
> +		root->rb_node = new;
> +}

I'm inclined to agree with Peter here - "inline" is now a vague,
pathetic and useless thing.  The problem is that the reader just
doesn't *know* whether or not the writer really wanted it to be
inlined.

If we have carefully made a decision to inline a function, we should
(now) use __always_inline.

If we have carefully made a decision to not inline a function, we
should use noinline.

If we don't care, we should omit all such markings.

This leaves no place for "inline"?


Marking it noinline shrinks the text by 60-odd bytes.  Given the number
of args, my gut feel is that this will be slower, despite the cache
benefit.  But that might be wrong.


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 2/9] rbtree: add __rb_change_child() helper function
Date: Mon, 20 Aug 2012 15:17:10 -0700	[thread overview]
Message-ID: <20120820151710.eeed9bcf.akpm@linux-foundation.org> (raw)
In-Reply-To: <1345500331-10546-3-git-send-email-walken@google.com>

On Mon, 20 Aug 2012 15:05:24 -0700
Michel Lespinasse <walken@google.com> wrote:

> Add __rb_change_child() as an inline helper function to replace code that
> would otherwise be duplicated 4 times in the source.
> 
> No changes to binary size or speed.
> 
> ...
>
> --- a/lib/rbtree.c
> +++ b/lib/rbtree.c
> @@ -66,6 +66,19 @@ static inline struct rb_node *rb_red_parent(struct rb_node *red)
>  	return (struct rb_node *)red->__rb_parent_color;
>  }
>  
> +static inline void
> +__rb_change_child(struct rb_node *old, struct rb_node *new,
> +		  struct rb_node *parent, struct rb_root *root)
> +{
> +	if (parent) {
> +		if (parent->rb_left == old)
> +			parent->rb_left = new;
> +		else
> +			parent->rb_right = new;
> +	} else
> +		root->rb_node = new;
> +}

I'm inclined to agree with Peter here - "inline" is now a vague,
pathetic and useless thing.  The problem is that the reader just
doesn't *know* whether or not the writer really wanted it to be
inlined.

If we have carefully made a decision to inline a function, we should
(now) use __always_inline.

If we have carefully made a decision to not inline a function, we
should use noinline.

If we don't care, we should omit all such markings.

This leaves no place for "inline"?


Marking it noinline shrinks the text by 60-odd bytes.  Given the number
of args, my gut feel is that this will be slower, despite the cache
benefit.  But that might be wrong.

--
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  reply	other threads:[~2012-08-20 22:17 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 [this message]
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
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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