From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 10 Aug 2001 14:30:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 10 Aug 2001 14:30:22 -0400 Received: from vasquez.zip.com.au ([203.12.97.41]:31752 "EHLO vasquez.zip.com.au") by vger.kernel.org with ESMTP id ; Fri, 10 Aug 2001 14:30:08 -0400 Message-ID: <3B742996.3F2C8DEC@zip.com.au> Date: Fri, 10 Aug 2001 11:36:06 -0700 From: Andrew Morton X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.7 i686) X-Accept-Language: en MIME-Version: 1.0 To: Subba Rao CC: Linux Kernel Subject: Re: Half Duplex and Zero Copy IP In-Reply-To: <20010810095313.A6219@home.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 Subba Rao wrote: > > Hello, > > I have 2 3Com NICs on my system. They are 3c905C Tornado PCI cards. > The drivers are compiled into the kernel (Slackware 8.0 with kernel 2.4.7). > > One of the interfaces will be used as a sniffer interface (without IP address) > and a very high traffic pipes. I do not wish to loose any packets coming to this > interface. Is it better if I initialize the interface in HALF DUPLEX mode? If yes, > how do I set the card to HALF DUPLEX mode? How can I find out the HW (NIC) settings > on the system? No, this will provide no benefit. > Another question about 3Com NICs, do they perform zero-copy IP? Linux's zerocopy infrastructure allows the sendfile() system call to save a copy with NICs which have hardware checksumming and scatter/gather. 3c905C is one such NIC. Kernel is not generally "zero copy", but large savings are available in certain situations. NFS packet reassembly benefits from 905C's as well. > I read that the performance improves a lot WITHOUT zero-copy IP. Not right. Where did you read that? -