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

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Message-ID: <20130530175559.7cbb6851@redhat.com>
Date:	Thu, 30 May 2013 17:55:59 +0200
From:	Jesper Dangaard Brouer <jbrouer@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	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 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).

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
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