From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nivedita Singhvi Subject: Re: UDP multicast packet loss not reported if TX ring overrun? Date: Mon, 17 Aug 2009 13:40:06 -0700 Message-ID: <4A89C026.4030402@us.ibm.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Eric Dumazet To: Christoph Lameter Return-path: Received: from e36.co.us.ibm.com ([32.97.110.154]:44716 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754767AbZHQUkV (ORCPT ); Mon, 17 Aug 2009 16:40:21 -0400 Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by e36.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id n7HKca8v020421 for ; Mon, 17 Aug 2009 14:38:36 -0600 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n7HKe8T2125814 for ; Mon, 17 Aug 2009 14:40:09 -0600 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n7HKe7ZH003534 for ; Mon, 17 Aug 2009 14:40:08 -0600 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Christoph Lameter wrote: > If I use a large send queue > > (echo 2000000 >/proc/sys/net/core/wmem_default) > > then lots of packet loss results if I try to send more packets than > the bandwidth of the wire (300 bytes the maximum rate is 341k pps). With a > size of 2M for the output buffer the TX ring is overrun. > > But this loss is nowhere seen in any counter increments: Is there any chance this is getting dropped at qdisc? Can you check with tc? thanks, Nivedita