Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751306AbWJPBkL (ORCPT ); Sun, 15 Oct 2006 21:40:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751304AbWJPBkK (ORCPT ); Sun, 15 Oct 2006 21:40:10 -0400 Received: from pool-72-66-199-112.ronkva.east.verizon.net ([72.66.199.112]:11973 "EHLO turing-police.cc.vt.edu") by vger.kernel.org with ESMTP id S1751298AbWJPBkJ (ORCPT ); Sun, 15 Oct 2006 21:40:09 -0400 Message-Id: <200610160139.k9G1dds0012638@turing-police.cc.vt.edu> X-Mailer: exmh version 2.7.2 01/07/2005 with nmh-1.2 To: Benjamin Herrenschmidt Cc: Jesse Huang , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, akpm@osdl.org, jgarzik@pobox.com Subject: Re: [PATCH 1/5] remove TxStartThresh and RxEarlyThresh In-Reply-To: Your message of "Mon, 16 Oct 2006 07:26:37 +1000." <1160947597.22522.3.camel@localhost.localdomain> From: Valdis.Kletnieks@vt.edu References: <1160855725.2266.1.camel@localhost.localdomain> <1160947597.22522.3.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1160962778_4950P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Sun, 15 Oct 2006 21:39:38 -0400 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2385 Lines: 55 --==_Exmh_1160962778_4950P Content-Type: text/plain; charset=us-ascii On Mon, 16 Oct 2006 07:26:37 +1000, Benjamin Herrenschmidt said: > Somebody patented FIFO thresholds ? Gack ? The US PTO is fundamentally busticated. http://www.engadget.com/2006/10/14/cisco-patents-the-triple-play/ Cisco got a patent on the concept of delivering voice, internet, and cable TV over one cable. Now admittedly, when they applied for it in 2000, it wasn't a buzzword yet - but I'm pretty sure that there was prior art. Back to the case at hand... In the case of the TxStartThresh and RxEarlyThresh, I don't think it's FIFO thresholds per se that are a problem - the note specifically mentioned cut-through, which is a specific technique of starting to deal with the alread-arrived head end of the packet *before* the tail end has arrived yet. e.g. if you read a packet that has 16 bytes of control info followed by 64 bytes of data, you have finished parsing the first 16 and have set stuff up by the time the 64 bytes starts arriving - even though you only started *one* read of 80 bytes). Of course, even *that* is an old technique - I remember discussion (and possibly implementation) of being able to read the front of an Ethernet packet, and do the routing table lookup fast enough so that you could start transmitting the packet on the outbound interface before it had finished arriving on the inbound. Of course, this was back when Proteon and Bay were start-ups, nobody did IP option fields or router ACLs or stuff like that, and level-3 routers were not much smarter (and perhaps stupider) than today's level-2 switches that filter/route based on MAC address... Maybe the patent is on the fact that you can't do cut-through routing well without enforcing certain relationships on the Rx and Tx FIFO thresholds... --==_Exmh_1160962778_4950P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFFMuLacC3lWbTT17ARAt/cAKDiQBdeCijkYUsjchqsyE9XM4og0QCeODTu MyEdOzs93nRFWCm291gzNQo= =yAFu -----END PGP SIGNATURE----- --==_Exmh_1160962778_4950P-- - 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/