From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next] fq_codel: report congestion notification at enqueue time Date: Fri, 29 Jun 2012 06:50:57 +0200 Message-ID: <1340945457.29822.7.camel@edumazet-glaptop> References: <1340903237.13187.151.camel@edumazet-glaptop> <1340907151.13187.169.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Nandita Dukkipati , netdev , Yuchung Cheng , codel@lists.bufferbloat.net, Matt Mathis , Neal Cardwell , David Miller To: Dave Taht Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: codel-bounces@lists.bufferbloat.net Errors-To: codel-bounces@lists.bufferbloat.net List-Id: netdev.vger.kernel.org On Thu, 2012-06-28 at 19:47 -0400, Dave Taht wrote: > On Thu, Jun 28, 2012 at 6:56 PM, Yuchung Cheng wrote: > > On Thu, Jun 28, 2012 at 11:12 AM, Eric Dumazet 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 NET_XMIT_SUCCESS. 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 queues) > 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 ;)