From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net 1/3] ixgbe: Fix issues with SR-IOV loopback when flow control is disabled Date: Mon, 19 Mar 2012 17:38:01 -0400 (EDT) Message-ID: <20120319.173801.655596594881567295.davem@davemloft.net> References: <1331975254-19443-1-git-send-email-jeffrey.t.kirsher@intel.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: alexander.h.duyck@intel.com, netdev@vger.kernel.org, gospo@redhat.com, sassmann@redhat.com To: jeffrey.t.kirsher@intel.com Return-path: Received: from shards.monkeyblade.net ([198.137.202.13]:39418 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755816Ab2CSViH (ORCPT ); Mon, 19 Mar 2012 17:38:07 -0400 In-Reply-To: <1331975254-19443-1-git-send-email-jeffrey.t.kirsher@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Jeff Kirsher Date: Sat, 17 Mar 2012 02:07:34 -0700 > From: Alexander Duyck > > This patch allows us to avoid a Tx hang when SR-IOV is enabled. This hang > can be triggered by sending small packets at a rate that was triggering Rx > missed errors from the adapter while the internal Tx switch and at least > one VF are enabled. > > This was all due to the fact that under heavy stress the Rx FIFO never > drained below the flow control high water mark. This resulted in the Tx > FIFO being head of line blocked due to the fact that it relies on the flow > control high water mark to determine when it is acceptable for the Tx to > place a packet in the Rx FIFO. > > The resolution for this is to set the FCRTH value to the RXPBSIZE - 32 so > that even if the ring is almost completely full we can still place Tx > packets on the Rx ring and drop incoming Rx traffic if we do not have > sufficient space available in the Rx FIFO. > > Signed-off-by: Alexander Duyck > Tested-by: Sibai Li > Signed-off-by: Jeff Kirsher Applied.