On Fri, 09 Sep 2016 14:29:38 -0700
John Fastabend <john.fastab...@gmail.com> wrote:
> e1000 supports a single TX queue so it is being shared with the stack
> when XDP runs XDP_TX action. This requires taking the xmit lock to
> ensure we don't corrupt the tx ring. To avoid taking and dropping the
> lock per packet this patch adds a bundling implementation to submit
> a bundle of packets to the xmit routine.
>
> I tested this patch running e1000 in a VM using KVM over a tap
> device using pktgen to generate traffic along with 'ping -f -l 100'.
>
> Suggested-by: Jesper Dangaard Brouer <bro...@redhat.com>
Thank you for actually implementing this! :-)
> Signed-off-by: John Fastabend <john.r.fastab...@intel.com>
> ---
[...]
> diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c
> b/drivers/net/ethernet/intel/e1000/e1000_main.c
> index 91d5c87..b985271 100644
> --- a/drivers/net/ethernet/intel/e1000/e1000_main.c
> +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
>
[...]
> @@ -3369,33 +3381,52 @@ static void e1000_tx_map_rxpage(struct e1000_tx_ring
> *tx_ring,
> }
>
> static void e1000_xmit_raw_frame(struct e1000_rx_buffer *rx_buffer_info,
> - unsigned int len,
> - struct net_device *netdev,
> - struct e1000_adapter *adapter)
> + __u32 len,
> + struct e1000_adapter *adapter,
> + struct e1000_tx_ring *tx_ring)
> {
> - struct netdev_queue *txq = netdev_get_tx_queue(netdev, 0);
> - struct e1000_hw *hw = &adapter->hw;
> - struct e1000_tx_ring *tx_ring;
> -
> if (len > E1000_MAX_DATA_PER_TXD)
> return;
>
> + if (E1000_DESC_UNUSED(tx_ring) < 2)
> + return;
> +
> + e1000_tx_map_rxpage(tx_ring, rx_buffer_info, len);
> + e1000_tx_queue(adapter, tx_ring, 0/*tx_flags*/, 1);
> +}
> +
> +static void e1000_xdp_xmit_bundle(struct e1000_rx_buffer_bundle *buffer_info,
> + struct net_device *netdev,
> + struct e1000_adapter *adapter)
> +{
> + struct netdev_queue *txq = netdev_get_tx_queue(netdev, 0);
> + struct e1000_tx_ring *tx_ring = adapter->tx_ring;
> + struct e1000_hw *hw = &adapter->hw;
> + int i = 0;
> +
> /* e1000 only support a single txq at the moment so the queue is being
> * shared with stack. To support this requires locking to ensure the
> * stack and XDP are not running at the same time. Devices with
> * multiple queues should allocate a separate queue space.
> + *
> + * To amortize the locking cost e1000 bundles the xmits and sends as
> + * many as possible until either running out of descriptors or failing.
> */
> HARD_TX_LOCK(netdev, txq, smp_processor_id());
>
> - tx_ring = adapter->tx_ring;
> -
> - if (E1000_DESC_UNUSED(tx_ring) < 2) {
> - HARD_TX_UNLOCK(netdev, txq);
> - return;
> + for (; i < E1000_XDP_XMIT_BUNDLE_MAX && buffer_info[i].buffer; i++) {
^^^
> + e1000_xmit_raw_frame(buffer_info[i].buffer,
> + buffer_info[i].length,
> + adapter, tx_ring);
> + buffer_info[i].buffer->rxbuf.page = NULL;
> + buffer_info[i].buffer = NULL;
> + buffer_info[i].length = 0;
> + i++;
^^^
Looks like "i" is incremented twice, is that correct?
> }
>
> - e1000_tx_map_rxpage(tx_ring, rx_buffer_info, len);
> - e1000_tx_queue(adapter, tx_ring, 0/*tx_flags*/, 1);
> + /* kick hardware to send bundle and return control back to the stack */
> + writel(tx_ring->next_to_use, hw->hw_addr + tx_ring->tdt);
> + mmiowb();
>
> writel(tx_ring->next_to_use, hw->hw_addr + tx_ring->tdt);
> mmiowb();
> @@ -4281,9 +4312,10 @@ static bool e1000_clean_jumbo_rx_irq(struct
> e1000_adapter *adapter,
> struct bpf_prog *prog;
> u32 length;
> unsigned int i;
> - int cleaned_count = 0;
> + int cleaned_count = 0, xdp_xmit = 0;
> bool cleaned = false;
> unsigned int total_rx_bytes = 0, total_rx_packets = 0;
> + struct e1000_rx_buffer_bundle *xdp_bundle = rx_ring->xdp_buffer;
>
> rcu_read_lock(); /* rcu lock needed here to protect xdp programs */
> prog = READ_ONCE(adapter->prog);
> @@ -4338,13 +4370,13 @@ static bool e1000_clean_jumbo_rx_irq(struct
> e1000_adapter *adapter,
> case XDP_PASS:
> break;
> case XDP_TX:
> + xdp_bundle[xdp_xmit].buffer = buffer_info;
> + xdp_bundle[xdp_xmit].length = length;
> dma_sync_single_for_device(&pdev->dev,
> dma,
> length,
> DMA_TO_DEVICE);
> - e1000_xmit_raw_frame(buffer_info, length,
> - netdev, adapter);
> - buffer_info->rxbuf.page = NULL;
> + xdp_xmit++;
> case XDP_DROP:
> default:
> /* re-use mapped page. keep buffer_info->dma
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
