[Codel] [PATCH net-next] fq_codel: report congestion notification at enqueue time

Eric Dumazet eric.dumazet at gmail.com
Fri Jun 29 00:50:57 EDT 2012

On Thu, 2012-06-28 at 19:47 -0400, Dave Taht wrote: 
> On Thu, Jun 28, 2012 at 6:56 PM, Yuchung Cheng <ycheng at google.com> wrote:
> > On Thu, Jun 28, 2012 at 11:12 AM, Eric Dumazet <eric.dumazet at gmail.com> wrote:
> >> On Thu, 2012-06-28 at 10:51 -0700, Dave Taht wrote:
> >>
> >>> clever idea. A problem is there are other forms of network traffic on
> >>> a link, and this is punishing a single tcp
> > Dave: it won't just punish a single TCP, all protocols that react to
> > XMIT_CN will share similar fate.
> What protocols in the kernel do and don't? was the crux of this question.

AFAIK that only tcp cares a bit, or seems to.

But not that much, since it continues to send packets.

Thats because tcp_transmit_skb() changes the NET_XMIT_CN status to plain

My long term plan is to reduce number of skbs queued in Qdisc for TCP
stack, to reduce RTT (removing the artificial RTT bias because of local

> I'm not objecting to the idea, it's clever, as I said. I'm thinking I'll
> apply it to cerowrt's next build and see what happens, if this
> will apply against 3.3. Or maybe the ns3 model. Or both.

A router will have no use of this feature, not sure you need to spend
time trying this ;)

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