From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-2.6 PATCH] ixgbe: fix automatic LRO/RSC settings for low latency Date: Sun, 13 Jun 2010 18:21:10 -0700 (PDT) Message-ID: <20100613.182110.112601110.davem@davemloft.net> References: <20100611224629.30958.22500.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, gospo@redhat.com, andy@greyhouse.net, sgruszka@redhat.com, stable@kernel.org To: jeffrey.t.kirsher@intel.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:58318 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753351Ab0FNBU7 (ORCPT ); Sun, 13 Jun 2010 21:20:59 -0400 In-Reply-To: <20100611224629.30958.22500.stgit@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: From: Jeff Kirsher Date: Fri, 11 Jun 2010 15:47:03 -0700 > From: Andy Gospodarek > > This patch added to 2.6.34: > > commit f8d1dcaf88bddc7f282722ec1fdddbcb06a72f18 > Author: Jesse Brandeburg > Date: Tue Apr 27 01:37:20 2010 +0000 > > ixgbe: enable extremely low latency > > introduced a feature where LRO (called RSC on the hardware) was disabled > automatically when setting rx-usecs to 0 via ethtool. Some might not > like the fact that LRO was disabled automatically, but I'm fine with > that. What I don't like is that LRO/RSC is automatically enabled when > rx-usecs is set >0 via ethtool. > > This would certainly be a problem if the device was used for forwarding > and it was determined that the low latency wasn't needed after the > device was already forwarding. I played around with saving the state of > LRO in the driver, but it just didn't seem worthwhile and would require > a small change to dev_disable_lro() that I did not like. > > This patch simply leaves LRO disabled when setting rx-usecs >0 and > requires that the user enable it again. An extra informational message > will also now appear in the log so users can understand why LRO isn't > being enabled as they expect. > > Inconsistency of LRO setting first noticed by Stanislaw Gruszka. > > Signed-off-by: Andy Gospodarek > CC: Stanislaw Gruszka > CC: stable@kernel.org > Tested-by: Stephen Ko > Signed-off-by: Jeff Kirsher Applied.