From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sridhar Samudrala Subject: Re: [RFC PATCH] Regression in linux 2.6.32 virtio_net seen with vhost-net Date: Wed, 16 Dec 2009 21:05:32 -0800 Message-ID: <4B29BC1C.7090800@us.ibm.com> References: <20091213122512.GA17255@gondor.apana.org.au> <200912161311.40644.rusty@rustcorp.com.au> <20091216025331.GA13935@gondor.apana.org.au> <200912162315.38802.rusty@rustcorp.com.au> <1261014180.11648.35.camel@w-sridhar.beaverton.ibm.com> <20091217031539.GA26087@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Rusty Russell , mst@redhat.com, netdev@vger.kernel.org To: Herbert Xu Return-path: Received: from e33.co.us.ibm.com ([32.97.110.151]:37885 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbZLQFFl (ORCPT ); Thu, 17 Dec 2009 00:05:41 -0500 Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by e33.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id nBH52jvP031493 for ; Wed, 16 Dec 2009 22:02:45 -0700 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 nBH55cfm188418 for ; Wed, 16 Dec 2009 22:05:38 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id nBH55b3T007796 for ; Wed, 16 Dec 2009 22:05:38 -0700 In-Reply-To: <20091217031539.GA26087@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: Herbert Xu wrote: > On Wed, Dec 16, 2009 at 05:43:00PM -0800, Sridhar Samudrala wrote: > >> I had to change virtnet_xmit_poll() to get it working. See below. >> With this change, i don't see any 'queue full' warnings, but requeues >> are still happening at the qdisc level (sch_direct_xmit() finds that >> tx queue is stopped and does requeues). >> > > Actually this makes no sense. The queue should only be stopped > at the end of a xmit run, in which case sch_direct_xmit should > return 0 so we should never see a requeue. > I think sch_direct_xmit() is not even calling dev_hard_start_xmit() as the tx queue is stopped and does a dev_requeue_skb() and returns NETDEV_TX_BUSY. > So if we're still seeing requeues then it hasn't been fixed > properly. > > Cheers, >