netdev - Re: [PATCH] net: increase skb->users instead of skb

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Date:	Thu, 16 Dec 2010 22:31:34 +0800
From:	Junchang Wang <junchangwang@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Changli Gao <xiaosuo@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Tom Herbert <therbert@...gle.com>,
	Jiri Pirko <jpirko@...hat.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Xinan Tang <xinan.tang@...el.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: increase skb->users instead of skb_clone()

On Thu, Dec 16, 2010 at 10:18 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> Yes, and no.
>
> Consider the case you have one receiver.
>
> Packet given after Changli patch wont be shared, so packet_rcv wont
> clone it : Thats a win. Only one skb_clone() done instead of two.
>
> Consider case with 2 receivers :
>
> First time we call packet_rcv, packet is shared (because we call
> deliver_skb(), so packet_rcv clones it. Normal situation, we really need
> to clone it.

Got it. Thanks.

>
> Second time, we give a non shared packet : Thats a win over previous
> situation.
>
But, if we have N receivers, we get only the last one win - the first N-1 will
call deliver_skb().


Thanks.
-- 
--Junchang
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