Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754763AbYKEGbc (ORCPT ); Wed, 5 Nov 2008 01:31:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750858AbYKEGbO (ORCPT ); Wed, 5 Nov 2008 01:31:14 -0500 Received: from mms3.broadcom.com ([216.31.210.19]:3503 "EHLO MMS3.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750754AbYKEGbN convert rfc822-to-8bit (ORCPT ); Wed, 5 Nov 2008 01:31:13 -0500 X-Server-Uuid: B55A25B1-5D7D-41F8-BC53-C57E7AD3C201 From: "Michael Chan" To: "'David Miller'" cc: "linux-kernel@blueteddy.net" , "daniel.blueman@gmail.com" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-net@vger.kernel.org" Date: Tue, 4 Nov 2008 22:31:00 -0800 Subject: Re: time for TCP ECN defaulting to on? Thread-Topic: time for TCP ECN defaulting to on? Thread-Index: Ack/C6LrNVSi8rKlSf+1crou6Oh01wAAs68A Message-ID: In-Reply-To: <20081104.215839.132524253.davem@davemloft.net> Accept-Language: en-US Content-Language: en-US acceptlanguage: en-US MIME-Version: 1.0 X-OriginalArrivalTime: 05 Nov 2008 06:31:01.0003 (UTC) FILETIME=[11F475B0:01C93F10] X-WSS-ID: 650FE22F37G9027923-01-01 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1106 Lines: 31 David Miller wrote: > From: "Michael Chan" > Date: Tue, 04 Nov 2008 17:16:03 -0800 > > > I think this is no longer a limitation. The GSO code will take care > > of ECN properly if the hardware does not support it when doing TSO. > > Hmm, good point, but if that is what happens I don't know if I agree > with it. > > If "take care of ECN" means doing TSO in software, that's in my > opinion the wrong thing to do. > Right, it means TSO will be done in software by the GSO code if ECE or CWR is set in a TSO frame and the driver indicates that the hardware cannot segment such packets properly. This allows TSO and ECN to coexist. Before this, ECN was always disabled when TSO was enabled. Assuming ECE and CWR are set infrequently on TSO frames, we still benefit from hardware TSO most of the time. Why is it the wrong thing to do? -- 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/