From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next 1/2] qdisc: Allow qdiscs to provide backpressure up the stack. Date: Thu, 26 Aug 2010 22:36:04 -0700 (PDT) Message-ID: <20100826.223604.48516081.davem@davemloft.net> References: <4C773BAF.7010809@candelatech.com> <20100826.213419.189712657.davem@davemloft.net> <4C774B8F.2030805@candelatech.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: greearb@candelatech.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:45066 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751130Ab0H0Fft (ORCPT ); Fri, 27 Aug 2010 01:35:49 -0400 In-Reply-To: <4C774B8F.2030805@candelatech.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Ben Greear Date: Thu, 26 Aug 2010 22:22:23 -0700 > On 08/26/2010 09:34 PM, David Miller wrote: >> From: Ben Greear >> Date: Thu, 26 Aug 2010 21:14:39 -0700 >> >>> I'll look into the NET_XMIT_CN, but if that propagates backpressure up >>> through mac-vlan, then something must know how to re-start the tx >>> logic. >> >> It doesn't need to, as it drops and frees up the packet. > > If there were 5 pkts in the socket buffer, and the attempt to > send the first one caused NET_XMIT_CN, then > based on your comment below about UDP being throttled, I assume > the other 4 are kept until later? It only has an effect on TCP, it causes it to decrease the congestion window limits. I did not state that it had any effect on UDP. Just because I talk about UDP later in my email doesn't mean the two things are related.