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Date: Wed, 8 Oct 2014 10:02:58 -0700
From: Greg Rose <gregory.v.rose@...el.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Daniel Borkmann <dborkman@...hat.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [PATCH net-next] i40e: skb->xmit_more support
On Tue, 7 Oct 2014 13:30:23 -0700
Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Support skb->xmit_more in i40e 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@...gle.com>
Looks good to me.
- Greg
> ---
> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 90 +++++++++---------
> 1 file changed, 46 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> b/drivers/net/ethernet/intel/i40e/i40e_txrx.c index
> 267992b3de8a..3195d82e4942 100644 ---
> a/drivers/net/ethernet/intel/i40e/i40e_txrx.c +++
> b/drivers/net/ethernet/intel/i40e/i40e_txrx.c @@ -2053,6 +2053,47 @@
> static void i40e_create_tx_ctx(struct i40e_ring *tx_ring, }
>
> /**
> + * __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
> + **/
> +#ifdef I40E_FCOE
> +int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> +#else
> +static int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> +#endif
> +{
> + if (likely(I40E_DESC_UNUSED(tx_ring) >= size))
> + return 0;
> + return __i40e_maybe_stop_tx(tx_ring, size);
> +}
> +
> +/**
> * i40e_tx_map - Build the Tx descriptor
> * @tx_ring: ring to send buffer on
> * @skb: send buffer
> @@ -2195,8 +2236,12 @@ static void i40e_tx_map(struct i40e_ring
> *tx_ring, struct sk_buff *skb,
> tx_ring->next_to_use = i;
>
> + i40e_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;
>
> @@ -2218,47 +2263,6 @@ 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
> - **/
> -#ifdef I40E_FCOE
> -int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> -#else
> -static int i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
> -#endif
> -{
> - 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
> @@ -2372,8 +2376,6 @@ 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:
>
>
> --
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