From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [PATCH net-next] ixgbe: flush when in xmit_more mode and under descriptor pressure Date: Tue, 26 Aug 2014 09:01:48 -0700 Message-ID: <53FCAF6C.2070401@intel.com> References: <1409068105-16634-1-git-send-email-dborkman@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org To: Daniel Borkmann Return-path: Received: from mga03.intel.com ([143.182.124.21]:47352 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858AbaHZQBu (ORCPT ); Tue, 26 Aug 2014 12:01:50 -0400 In-Reply-To: <1409068105-16634-1-git-send-email-dborkman@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 08/26/2014 08:48 AM, Daniel Borkmann wrote: > When xmit_more mode is being used and the ring is about to become > full, enforce a tail pointer write to the hw. Otherwise, we could > risk a Tx hang as pointed out by Alex. > > Suggested-by: Alexander Duyck > Signed-off-by: Daniel Borkmann > --- > Hi Alex, something along that lines regarding your first comment? > > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 67 +++++++++++++++------------ > 1 file changed, 38 insertions(+), 29 deletions(-) > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > index ba9ceaa..f851e84 100644 > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c > @@ -6853,6 +6883,7 @@ static void ixgbe_tx_map(struct ixgbe_ring *tx_ring, > u32 tx_flags = first->tx_flags; > u32 cmd_type = ixgbe_tx_cmd_type(skb, tx_flags); > u16 i = tx_ring->next_to_use; > + bool desc_pressure; > > tx_desc = IXGBE_TX_DESC(tx_ring, i); > > @@ -6958,10 +6989,15 @@ static void ixgbe_tx_map(struct ixgbe_ring *tx_ring, > > tx_ring->next_to_use = i; > > - if (!skb->xmit_more) { > + desc_pressure = (ixgbe_desc_unused(tx_ring) < DESC_NEEDED); > + if (!skb->xmit_more || unlikely(desc_pressure)) { > /* notify HW of packet */ > ixgbe_write_tail(tx_ring, i); > + > + if (unlikely(desc_pressure)) > + __ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED); > } > + > return; > dma_error: > dev_err(tx_ring->dev, "TX DMA map failed\n"); > @@ -6978,6 +7014,7 @@ dma_error: > } > > tx_ring->next_to_use = i; > + ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED); > } > Actually this bit here is much more complicated than it probably needs to be. My thought is to just fold ixgbe_maybe_stop_tx into the if statement. So it shoudl be: if (!skb->smit_more || ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED)) If the BQL bit is folded into the xmit_more check somewhere then that should be enough to resolve any possible ring stalls. Thanks, Alex