From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Banks Subject: Re: [PATCH] fix BUG in tg3_tx Date: Thu, 27 May 2004 09:50:08 +1000 Sender: netdev-bounce@oss.sgi.com Message-ID: <20040526235008.GB5958@sgi.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , netdev@oss.sgi.com Return-path: To: Michael Chan Content-Disposition: inline In-Reply-To: Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Wed, May 26, 2004 at 10:43:10AM -0700, Michael Chan wrote: > > > [...] is there a good reason why the tg3 driver > > uses the on-chip SRAM send ring by default instead of the > > host send ring?[...] > > I can only speak for the Broadcom bcm5700 driver. We used to use NIC > send BDs by default before zero copy transmit and TSO were implemented > in the kernel. Using only one BD per packet at that time, we found that > performance on some machines were sometimes slightly better. Especially > with logic to save some PIO when some of the fields in the BD have not > changed. The driver has now been changed to use host send BDs to perform > better with zero copy and especially TSO where you may need many BDs per > packet. I would recommend tg3 to make the switch also. Ah, it's precisely the zero copy case I'm interested in. I've measured 2 to 3 BDs per packet under my load. Greg. -- Greg Banks, R&D Software Engineer, SGI Australian Software Group. I don't speak for SGI.