From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030264AbWFAUHM (ORCPT ); Thu, 1 Jun 2006 16:07:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030265AbWFAUHM (ORCPT ); Thu, 1 Jun 2006 16:07:12 -0400 Received: from mailout1.vmware.com ([65.113.40.130]:31237 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S1030264AbWFAUHK (ORCPT ); Thu, 1 Jun 2006 16:07:10 -0400 Message-ID: <447F48ED.6090202@vmware.com> Date: Thu, 01 Jun 2006 13:07:09 -0700 From: Zachary Amsden User-Agent: Thunderbird 1.5.0.2 (X11/20060420) MIME-Version: 1.0 To: Andrew Morton Cc: manfred@colorfullife.com, linux-kernel@vger.kernel.org, Ayaz Abdulla Subject: Re: [PATCH] Allow TSO to be disabled for forcedeth driver References: <447F3FB8.2010003@vmware.com> <20060601125359.10ca1f2b.akpm@osdl.org> In-Reply-To: <20060601125359.10ca1f2b.akpm@osdl.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > Zachary Amsden wrote: > >> TSO can cause performance problems in certain environments, and being >> able to turn it on or off is helpful for debugging network issues. Most >> other network drivers that support TSO allow it to be toggled, so add >> this feature to forcedeth. Tested by Harald Dunkel, who reported that >> this fixed his network performance issue with VMware. >> >> > > (This is regarding > http://www.vmware.com/community/thread.jspa?messageID=408893) > > > Why does TSO-with-forcedeth make vmware networking slow? > > Is it specific to the forcedeth driver? > No. TSO is not good for bridged virtual networking in general, since even if the bridged networking module understood TSO, it would then have to split up any large packets into smaller packets to pass on to the guest virtual machine - or require that the guest virtual machine have and understand how to use a TSO compatible network interface as well. Both solutions are extremely problematic, and the easiest thing to do is just disable TSO. It makes sense for any protocol bridge device, including some firewall configurations. Zach