netdev - Re: [PATCH RFC 00/14] shrink skb cb to 44 bytes

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Message-Id: <20150302.171747.1423128180512348489.davem@davemloft.net>
Date:	Mon, 02 Mar 2015 17:17:47 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	fw@...len.de, netdev@...r.kernel.org, johannes@...solutions.net,
	linux-wireless@...r.kernel.org
Subject: Re: [PATCH RFC 00/14] shrink skb cb to 44 bytes

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 02 Mar 2015 11:49:23 -0800

> Size of skb->cb[] is not the major factor. Trying to gain 4 or 8 bytes
> is not going to improve performance a lot.
> 
> The real problem is that we clear it in skb_alloc()/build_skb(), instead
> of each layer doing so at demand, and only the part that matters for
> this layer.
> 
> Basically, skb->cb[] could be 80 or 160 bytes instead of 48, and we
> should not care, as long as no layer does a stupid/lazy 
> 
> memset(skb->cb, 0, sizeof(skb->cb))
> 
> Presumably skb_clone() could be extended to receive the length of
> skb->cb[] that current layer cares about.

Regardless, I think Florian's work has value.
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