linux-kernel - Re: [PATCH] include:linux:Optimizations to __skb

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Message-ID: <CA+mtBx8yeLG7UwqtknAsUTBtpocspraBcfj5W-2vTBA5pC8LEQ@mail.gmail.com>
Date:	Thu, 22 Jan 2015 10:21:47 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Mohammad Jamal <md.jamalmohiuddin@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, viro@...iv.linux.org.uk,
	Alexander Duyck <alexander.h.duyck@...hat.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] include:linux:Optimizations to __skb_push

On Thu, Jan 22, 2015 at 10:02 AM, Mohammad Jamal
<md.jamalmohiuddin@...il.com> wrote:
> This patch optimizes __skb_push function
>
> Signed-off-by: Mohammad Jamal <md.jamalmohiuddin@...il.com>
> ---
>  include/linux/skbuff.h |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 85ab7d7..9acffb2 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1671,9 +1671,8 @@ static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
>  unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
>  static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
>  {
> -       skb->data -= len;
>         skb->len  += len;
> -       return skb->data;
> +       return skb->data -= len;
>  }
>
Hmm, this seems less readable to me. What is the effect of this patch?
Does the compiler even produce different assembly?

Thanks,
Tom

>  unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
> --
> 1.7.9.5
>
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