Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754090Ab0KYQZp (ORCPT ); Thu, 25 Nov 2010 11:25:45 -0500 Received: from mail.lysator.liu.se ([130.236.254.3]:42143 "EHLO mail.lysator.liu.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753649Ab0KYQZo (ORCPT ); Thu, 25 Nov 2010 11:25:44 -0500 From: nisse@lysator.liu.se (Niels =?iso-8859-1?Q?M=F6ller?=) To: Eric Dumazet Cc: linux-kernel@vger.kernel.org, netdev Subject: Re: TCP_MAXSEG vs TCP/generic segmentation offload (tso/gso) References: <1290695253.2858.336.camel@edumazet-laptop> <1290698312.2858.341.camel@edumazet-laptop> Date: Thu, 25 Nov 2010 17:25:42 +0100 In-Reply-To: <1290698312.2858.341.camel@edumazet-laptop> (Eric Dumazet's message of "Thu, 25 Nov 2010 16:18:31 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (usg-unix-v) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1273 Lines: 30 Eric Dumazet writes: > I believe TCP_MAXSEG is working fine, but GRO/GSO dont care at all : > They coalesce frames whatever their size is. I was under the impression that TSO (and maybe GSO) implied more cleverness in the network card; that the network card more or less gets to decide by itself how to divide a tcp stream into segments. And for example in the atl1c driver which I looked a bit into, this was what the REG_MTU register was for. Seems I have gotten this totally wrong. Maybe Documentation/networking/netdevices.txt could clarify how it works. Currently, it says : Segmentation Offload (GSO, TSO) is an exception to this rule. The : upper layer protocol may pass a large socket buffer to the device : transmit routine, and the device will break that up into separate : packets based on the current MTU. Regards, and thanks for your patience, /Niels -- Niels M?ller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance. -- 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/