On Mon, 22 Jun 2020 12:21:11 +0300 Denis Kirjanov <k...@linux-powerpc.org>
wrote:
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 482c6c8..1b9f49e 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
[...]
> @@ -560,6 +572,65 @@ static u16 xennet_select_queue(struct net_device *dev,
> struct sk_buff *skb,
> return queue_idx;
> }
>
> +static int xennet_xdp_xmit_one(struct net_device *dev, struct xdp_frame
> *xdpf)
> +{
> + struct netfront_info *np = netdev_priv(dev);
> + struct netfront_stats *tx_stats = this_cpu_ptr(np->tx_stats);
> + unsigned int num_queues = dev->real_num_tx_queues;
> + struct netfront_queue *queue = NULL;
> + struct xen_netif_tx_request *tx;
> + unsigned long flags;
> + int notify;
> +
> + queue = &np->queues[smp_processor_id() % num_queues];
> +
> + spin_lock_irqsave(&queue->tx_lock, flags);
Why are you taking a lock per packet (xdp_frame)?
> +
> + tx = xennet_make_first_txreq(queue, NULL,
> + virt_to_page(xdpf->data),
> + offset_in_page(xdpf->data),
> + xdpf->len);
> +
> + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
> + if (notify)
> + notify_remote_via_irq(queue->tx_irq);
> +
> + u64_stats_update_begin(&tx_stats->syncp);
> + tx_stats->bytes += xdpf->len;
> + tx_stats->packets++;
> + u64_stats_update_end(&tx_stats->syncp);
> +
> + xennet_tx_buf_gc(queue);
> +
> + spin_unlock_irqrestore(&queue->tx_lock, flags);
Is the irqsave/irqrestore variant really needed here?
> + return 0;
> +}
> +
> +static int xennet_xdp_xmit(struct net_device *dev, int n,
> + struct xdp_frame **frames, u32 flags)
> +{
> + int drops = 0;
> + int i, err;
> +
> + if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
> + return -EINVAL;
> +
> + for (i = 0; i < n; i++) {
> + struct xdp_frame *xdpf = frames[i];
> +
> + if (!xdpf)
> + continue;
> + err = xennet_xdp_xmit_one(dev, xdpf);
> + if (err) {
> + xdp_return_frame_rx_napi(xdpf);
> + drops++;
> + }
> + }
> +
> + return n - drops;
> +}
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
