提交 5804283d 编写于 作者: E Eric Dumazet 提交者: David S. Miller

mlx4: exploit skb->xmit_more to conditionally send doorbell

skb->xmit_more tells us if another skb is coming next.

We need to send doorbell when : xmit_more is not set,
or txqueue is stopped (preventing next skb to come immediately)

Tested with a modified pktgen version, I got a 40% increase of
throughput.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
上级 a8404ce5
......@@ -667,6 +667,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
int lso_header_size;
void *fragptr;
bool bounce = false;
bool send_doorbell;
if (!priv->port_up)
goto tx_drop;
......@@ -878,12 +879,16 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
skb_tx_timestamp(skb);
if (ring->bf_enabled && desc_size <= MAX_BF && !bounce && !vlan_tx_tag_present(skb)) {
send_doorbell = !skb->xmit_more || netif_xmit_stopped(ring->tx_queue);
if (ring->bf_enabled && desc_size <= MAX_BF && !bounce &&
!vlan_tx_tag_present(skb) && send_doorbell) {
tx_desc->ctrl.bf_qpn |= cpu_to_be32(ring->doorbell_qpn);
op_own |= htonl((bf_index & 0xffff) << 8);
/* Ensure new descirptor hits memory
* before setting ownership of this descriptor to HW */
/* Ensure new descriptor hits memory
* before setting ownership of this descriptor to HW
*/
wmb();
tx_desc->ctrl.owner_opcode = op_own;
......@@ -896,12 +901,16 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
ring->bf.offset ^= ring->bf.buf_size;
} else {
/* Ensure new descirptor hits memory
* before setting ownership of this descriptor to HW */
/* Ensure new descriptor hits memory
* before setting ownership of this descriptor to HW
*/
wmb();
tx_desc->ctrl.owner_opcode = op_own;
wmb();
iowrite32be(ring->doorbell_qpn, ring->bf.uar->map + MLX4_SEND_DOORBELL);
if (send_doorbell) {
wmb();
iowrite32be(ring->doorbell_qpn,
ring->bf.uar->map + MLX4_SEND_DOORBELL);
}
}
return NETDEV_TX_OK;
......
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