netdev - Re: [RFC] truesize lies

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Message-Id: <20111009.172739.2151675769111763947.davem@davemloft.net>
Date:	Sun, 09 Oct 2011 17:27:39 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] truesize lies

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 09 Oct 2011 21:02:28 +0200

> I guess most driver writers adjust truesize to please TCP stack and get
> nice performance numbers.
> 
> skb->truesize = frame_len + sizeof(sk_buff);
> 
> What should we do exactly ?

We should pick a specification that accounts for all the metadata as well
as unused data areas properly, and enforce this in netif_receive_skb().

That will get the inaccurate cases fixed real fast.

We've had similar problems in the past and dealt with it in the same
exact way.
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