From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [PATCH 2/2] ixgbe: support skb->xmit_more in netdev_ops->ndo_start_xmit() Date: Tue, 26 Aug 2014 08:00:10 -0700 Message-ID: <53FCA0FA.20600@intel.com> References: <20140825.163505.1969688661687017343.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: therbert@google.com, jhs@mojatatu.com, hannes@stressinduktion.org, edumazet@google.com, jeffrey.t.kirsher@intel.com, rusty@rustcorp.com.au, dborkman@redhat.com, brouer@redhat.com To: David Miller , netdev@vger.kernel.org Return-path: Received: from mga03.intel.com ([143.182.124.21]:17016 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758273AbaHZPAU (ORCPT ); Tue, 26 Aug 2014 11:00:20 -0400 In-Reply-To: <20140825.163505.1969688661687017343.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On 08/25/2014 04:35 PM, David Miller wrote: > > From: Daniel Borkmann > > This implements the deferred tail pointer flush API for the ixgbe > driver. Similar version also proposed longer time ago by Alexander Duyck. > > Signed-off-by: Daniel Borkmann > Signed-off-by: David S. Miller > --- > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > index 87bd53f..ba9ceaa 100644 > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > @@ -6958,9 +6958,10 @@ static void ixgbe_tx_map(struct ixgbe_ring *tx_ring, > > tx_ring->next_to_use = i; > > - /* notify HW of packet */ > - ixgbe_write_tail(tx_ring, i); > - > + if (!skb->xmit_more) { > + /* notify HW of packet */ > + ixgbe_write_tail(tx_ring, i); > + } > return; > dma_error: > dev_err(tx_ring->dev, "TX DMA map failed\n"); > It might help to add some handling for the case where xmit_more is set, but the ring has become full. This current implementation introduces the risk of triggering a Tx hang. My advice would be to pull the ixgbe_maybe_stop_tx code at the end of xmit_frame into the if check here, and perhaps look into adding an additional check to see if BQL has stopped the ring as well. Thanks, Alex