netdev - Re: [PATCH -next] net: core: set qdisc pkt len before tc

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Date:	Wed, 13 May 2015 07:07:47 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Florian Westphal <fw@...len.de>
CC:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
	daniel@...earbox.net
Subject: Re: [PATCH -next] net: core: set qdisc pkt len before tc_classify

On 05/13/15 07:02, Jamal Hadi Salim wrote:
>
>
> I dont think we need the stab on the ingress but we do need to account
> for gso. So option #1 with qdisc_pkt_len_init() alone is the only thing
> needed. i.e Florian's change becomes:
>
> -    qdisc_bstats_update_cpu(cl->q, skb);
> +    qdisc_pkt_len_init(skb)
>       skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_INGRESS);
> +    qdisc_bstats_update_cpu(cl->q, skb);
>
> Alexei, why do you say this option will have overhead?
>

and the comment in qdisc_pkt_len_init() needs fixing too.
It says:
         /* To get more precise estimation of bytes sent on wire,
          * we add to pkt_len the headers size of all segments
          */


It implies transmit direction only - modern nics do set this
on receive.  Something like:

         /* To get more precise estimation of bytes rx or to be sent
           on the wire, we add to pkt_len the headers size of
           all segments
         */

cheers,
jamal
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