[Intel-wired-lan] [net-next S4 12/15] i40evf: skb->xmit_more support

[Alexander Duyck <alexander.h.duyck@redhat.com>]

On 04/16/2015 05:06 PM, Catherine Sullivan wrote:
> From: Jesse Brandeburg <jesse.brandeburg@intel.com>
>
> Eric added support for skb->xmit_more in i40e, this ports that into i40evf as well.
>
> Support skb->xmit_more in i40evf is straightforward; we need to move
> around i40e_maybe_stop_tx() call to correctly test netif_xmit_stopped()
> before taking the decision to not kick the NIC.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
> Change-ID: Idddda6a2e4a7ab335631c91ced51f55b25eb8468
> ---

This patch description is confusing.  Maybe you should include and 
indent the original patch description from what you are porting into the 
VF rather than just including the Signed-off-by from the original 
patch.  At first I thought Eric was helping to port the patch and had 
contributed code to the porting effort.  Also Daniel's email address is 
no longer valid so you probably shouldn't be Ccing the message to him.

>   drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 88 ++++++++++++++-------------
>   1 file changed, 47 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> index e1a44dd..4f77d38 100644
> --- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> @@ -1672,6 +1672,47 @@ linearize_chk_done:
>   }
>   
>   /**
> + * __i40evf_maybe_stop_tx - 2nd level check for tx stop conditions
> + * @tx_ring: the ring to be checked
> + * @size:    the size buffer we want to assure is available
> + *
> + * Returns -EBUSY if a stop is needed, else 0
> + **/
> +static inline int __i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> +{
> +	netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
> +	/* Memory barrier before checking head and tail */
> +	smp_mb();
> +
> +	/* Check again in a case another CPU has just made room available. */
> +	if (likely(I40E_DESC_UNUSED(tx_ring) < size))
> +		return -EBUSY;
> +
> +	/* A reprieve! - use start_queue because it doesn't call schedule */
> +	netif_start_subqueue(tx_ring->netdev, tx_ring->queue_index);
> +	++tx_ring->tx_stats.restart_queue;
> +	return 0;
> +}
> +
> +/**
> + * i40evf_maybe_stop_tx - 1st level check for tx stop conditions
> + * @tx_ring: the ring to be checked
> + * @size:    the size buffer we want to assure is available
> + *
> + * Returns 0 if stop is not needed
> + **/
> +#ifdef I40E_FCOE
> +int i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> +#else
> +static int i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> +#endif
> +{
> +	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
> +		return 0;
> +	return __i40evf_maybe_stop_tx(tx_ring, size);
> +}
> +
> +/**

I didn't think the VF could do FCoE can it?

>    * i40e_tx_map - Build the Tx descriptor
>    * @tx_ring:  ring to send buffer on
>    * @skb:      send buffer
> @@ -1808,8 +1849,12 @@ static void i40e_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
>   
>   	tx_ring->next_to_use = i;
>   
> +	i40evf_maybe_stop_tx(tx_ring, DESC_NEEDED);
>   	/* notify HW of packet */
> -	writel(i, tx_ring->tail);
> +	if (!skb->xmit_more ||
> +	    netif_xmit_stopped(netdev_get_tx_queue(tx_ring->netdev,
> +						   tx_ring->queue_index)))
> +		writel(i, tx_ring->tail);
>   
>   	return;
>   

You might want to just add a helper macro to take care of all of the 
netdev_get_tx_queue stuff, it would help readability.

> @@ -1831,43 +1876,6 @@ dma_error:
>   }
>   
>   /**
> - * __i40e_maybe_stop_tx - 2nd level check for tx stop conditions
> - * @tx_ring: the ring to be checked
> - * @size:    the size buffer we want to assure is available
> - *
> - * Returns -EBUSY if a stop is needed, else 0
> - **/
> -static inline int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> -{
> -	netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
> -	/* Memory barrier before checking head and tail */
> -	smp_mb();
> -
> -	/* Check again in a case another CPU has just made room available. */
> -	if (likely(I40E_DESC_UNUSED(tx_ring) < size))
> -		return -EBUSY;
> -
> -	/* A reprieve! - use start_queue because it doesn't call schedule */
> -	netif_start_subqueue(tx_ring->netdev, tx_ring->queue_index);
> -	++tx_ring->tx_stats.restart_queue;
> -	return 0;
> -}
> -
> -/**
> - * i40e_maybe_stop_tx - 1st level check for tx stop conditions
> - * @tx_ring: the ring to be checked
> - * @size:    the size buffer we want to assure is available
> - *
> - * Returns 0 if stop is not needed
> - **/
> -static int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> -{
> -	if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
> -		return 0;
> -	return __i40e_maybe_stop_tx(tx_ring, size);
> -}
> -
> -/**
>    * i40e_xmit_descriptor_count - calculate number of tx descriptors needed
>    * @skb:     send buffer
>    * @tx_ring: ring to send buffer on
> @@ -1892,7 +1900,7 @@ static int i40e_xmit_descriptor_count(struct sk_buff *skb,
>   		count += TXD_USE_COUNT(skb_shinfo(skb)->frags[f].size);
>   
>   	count += TXD_USE_COUNT(skb_headlen(skb));
> -	if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
> +	if (i40evf_maybe_stop_tx(tx_ring, count + 4 + 1)) {
>   		tx_ring->tx_stats.tx_busy++;
>   		return 0;
>   	}
> @@ -1968,8 +1976,6 @@ static netdev_tx_t i40e_xmit_frame_ring(struct sk_buff *skb,
>   	i40e_tx_map(tx_ring, skb, first, tx_flags, hdr_len,
>   		    td_cmd, td_offset);
>   
> -	i40e_maybe_stop_tx(tx_ring, DESC_NEEDED);
> -
>   	return NETDEV_TX_OK;
>   
>   out_drop: