Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 6 Oct 2001 06:00:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 6 Oct 2001 05:59:52 -0400 Received: from cs82093.pp.htv.fi ([212.90.82.93]:21376 "EHLO cs82093.pp.htv.fi") by vger.kernel.org with ESMTP id ; Sat, 6 Oct 2001 05:59:42 -0400 Message-ID: <3BBED618.768332@welho.com> Date: Sat, 06 Oct 2001 12:59:52 +0300 From: Mika Liljeberg X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.10 i686) X-Accept-Language: en MIME-Version: 1.0 To: "David S. Miller" CC: cwidmer@iiic.ethz.ch, linux-kernel@vger.kernel.org Subject: Re: unnecessary retransmit from network stack In-Reply-To: <200110051229.f95CTvN00624@mail.swissonline.ch> <20011005.161105.78709492.davem@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "David S. Miller" wrote: > > From: Christian Widmer > Date: Fri, 5 Oct 2001 14:29:53 +0200 > > why does net_dev.hard_start_xmit get called multiple times > with the same tcp packet? > > Because the ACK is not coming back for those packets within the RTO > (which for a local network is very low). Check your TCP dumps, > the ACKs of the original data packets are being dropped in transit. Well, TCP certainly shouldn't be sending two retransmissions back-to-back within 2ms, especially with nothing received in between. Not with RTO (which in Linux is never below 20ms, and according to RFC should be conservatively rounded up to 1 second), nor with fast retransmits or SACK. Just an observation. MikaL - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/