From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Subject: Re: [RFC] truesize lies
Date: Sun, 09 Oct 2011 23:55:20 +0200 [thread overview]
Message-ID: <1318197320.21116.11.camel@edumazet-laptop> (raw)
In-Reply-To: <20111009.172739.2151675769111763947.davem@davemloft.net>
Le dimanche 09 octobre 2011 à 17:27 -0400, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@gmail.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.
Some drivers splits a page in two (or more) pieces, so we cant know what
was really reserved by a driver for paged skbs.
Only thing we could enforce at the moment is the proper accounting for
skb head :
WARN_ON(skb->truesize < (skb_end_pointer(skb) - skb->head) + sizeof(sk_buff) + skb->data_len);
next prev parent reply other threads:[~2011-10-09 21:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-09 19:02 [RFC] truesize lies Eric Dumazet
2011-10-09 19:25 ` Andi Kleen
2011-10-09 21:27 ` David Miller
2011-10-09 21:55 ` Eric Dumazet [this message]
2011-10-09 22:10 ` David Miller
2011-10-10 6:54 ` Eric Dumazet
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