netdev - Re: tc linklayer ADSL calc broken after commit 56b765b79 (htb: improved accuracy at high rates)

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Date:	Thu, 30 May 2013 19:29:06 +0300
From:	Jussi Kivilinna <jussi.kivilinna@....fi>
To:	Jesper Dangaard Brouer <jbrouer@...hat.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	David Miller <davem@...hat.com>, j.vimal@...il.com,
	Michal Soltys <soltys@....info>,
	Mike Frysinger <vapier@...too.org>,
	Jussi Kivilinna <jussi.kivilinna@...et.fi>,
	Patrick McHardy <kaber@...sh.net>,
	Jiri Pirko <jpirko@...hat.com>,
	Toke Høiland-Jørgensen 
	<toke@...e.dk>, Dave Taht <dave.taht@...il.com>,
	netdev@...r.kernel.org, bloat@...ts.bufferbloat.net,
	Dan Siemon <dan@...erfire.com>,
	Jim Gettys <jg@...edesktop.org>,
	Steven Barth <cyrus@...nwrt.org>, Felix Fietkau <nbd@....name>,
	Jiri Benc <jbenc@...hat.com>
Subject: Re: tc linklayer ADSL calc broken after commit 56b765b79 (htb: improved
 accuracy at high rates)

On 30.05.2013 18:55, Jesper Dangaard Brouer wrote:
> On Thu, 30 May 2013 07:39:10 -0700
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
>> On Thu, 2013-05-30 at 09:51 +0200, Jesper Dangaard Brouer wrote:
>>> On Wed, 29 May 2013 08:52:04 -0700
>>> Eric Dumazet <eric.dumazet@...il.com> wrote:
>>
>>>> I am not sure it will solve the ATM logic (with the 5 bytes
>>>> overhead per 48 bytes cell)
>>>
>>> Are you talking about, that for GSO frames we are not adding a encap
>>> overhead to each "sub" skb.
>>
>> This part is now done properly in qdisc_pkt_len_init() since linux-3.9
> 
> Thanks for the pointer, but qdisc_pkt_len_init() only adds the
> EthMAC+IP+TCP header size for each GSO segment (stored in
> qdisc_skb_cb(skb)->pkt_len).
> It is still missing the AAL5 encapsulation overhead per GSO segment.
> 
> Besides I can see that __qdisc_calculate_pkt_len() "forgets" this
> information and overwrites qdisc_skb_cb(skb)->pkt_len (iif a stab is
> defined on the qdisc).
> 

Maybe change qdisc_pkt_len_init() to take the additional overhead value as
input and change __qdisc_calculate_pkt_len() use

	qdisc_pkt_len_init(skb, stab->szopts.overhead);

instead of

	pkt_len = skb->len + stab->szopts.overhead;

-Jussi
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