From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next-2.6 PATCH 2/5] ixgbe: drop support for UDP in RSS hash generation Date: Mon, 19 Jul 2010 23:44:54 -0700 (PDT) Message-ID: <20100719.234454.123445936.davem@davemloft.net> References: <20100719235831.14112.14175.stgit@localhost.localdomain> <20100719235925.14112.65890.stgit@localhost.localdomain> <1279607980.2458.82.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: jeffrey.t.kirsher@intel.com, netdev@vger.kernel.org, gospo@redhat.com, bphilips@novell.com, alexander.h.duyck@intel.com, donald.c.skidmore@intel.com To: eric.dumazet@gmail.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:57710 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754398Ab0GTGoi (ORCPT ); Tue, 20 Jul 2010 02:44:38 -0400 In-Reply-To: <1279607980.2458.82.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Tue, 20 Jul 2010 08:39:40 +0200 > This would be a serious regression. The regression is in the hardware Eric. > Many UDP applications try hard to not use fragments. > > They are going to pay the price because some application : > - Use big segments, fragmented. > - Is subject to OOO artifacts. None of this matters. If the hardware can't flow seperate properly it's tough cookies. We never may reorder packets in our stack by our own doing. The only safe default is to turn UDP flow seperation off on chips like ixgbe. If you want an ethtool knob to turn it back on for your machines, fine. But never can it be enabled by default.