From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966146AbXG3RAz (ORCPT ); Mon, 30 Jul 2007 13:00:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936408AbXG3RAo (ORCPT ); Mon, 30 Jul 2007 13:00:44 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:53117 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933851AbXG3RAm (ORCPT ); Mon, 30 Jul 2007 13:00:42 -0400 Date: Mon, 30 Jul 2007 12:00:40 -0500 To: Jan-Bernd Themann Cc: netdev , Thomas Klein , Jeff Garzik , Jan-Bernd Themann , linux-kernel , linux-ppc , Christoph Raisch , Marcus Eder , Andrew Gallatin , Stefan Roscher , David Miller Subject: Re: [PATCH 0/4][RFC] lro: Generic Large Receive Offload for TCP traffic Message-ID: <20070730170038.GA4884@austin.ibm.com> References: <200707301724.33865.ossthema@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200707301724.33865.ossthema@de.ibm.com> User-Agent: Mutt/1.5.11 From: linas@austin.ibm.com (Linas Vepstas) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 30, 2007 at 05:24:33PM +0200, Jan-Bernd Themann wrote: > > Changes to http://www.spinics.net/lists/netdev/msg36912.html > > 1) A new field called "features" has been added to the net_lro_mgr struct. > It is set by the driver to indicate: > - LRO_F_NAPI: Use NAPI / netif_rx to pass packets to stack > > - LRO_F_EXTRACT_VLAN_ID: Set by driver if HW extracts VLAN IDs for VLAN > packets but does not modify ETH protocol (ETH_P_8021Q) > > 2) Padded frames are not aggregated for now. Bug fixed > > 3) Correct header length now used. No minimal header length for aggregated > packets used anymore. > > 4) Statistic counters were introduced. They are stored in a new struct in > the net_lro_mgr. This has the advantage that no locking is required in > cases where the driver uses multiple lro_mgrs for different receive queues. > Thus we get the following statistics per lro_mgr / eth device: > - Number of aggregated packets > - Number of flushed packets > - Number of times we run out of lro_desc. > > The ratio of "aggregated packets" and "flushed packets" give you an > idea how well LRO is working. I'd like to see an edited form of this, together with an introduction to LRO, written up in the Documentation subdirectory. As someone with some driver experience, but not on te bleeding edge, some basc newbie questions pop into mind: -- what is LRO? -- Basic principles of operation? -- Can I use it in my driver? -- Does my hardware have to have some special feature before I can use it? -- What sort of performance improvement does it provide? Throughput? Latency? CPU usage? How does it affect DMA allocation? Does it improve only a certain type of traffic (large/small packets, etc.) -- Example code? What's the API? How should my driver use it? Right now, I can maybe find answers by doing lots of googling. I'd like to have some quick way of getting a grip on this. --linas