netdev - Re: [PATCH net-next v4 07/10] virtio-net: virtnet_poll

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Date:   Wed, 14 Apr 2021 11:34:07 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org,
        "dust . li" <dust.li@...ux.alibaba.com>
Subject: Re: [PATCH net-next v4 07/10] virtio-net: virtnet_poll_tx support
 budget check


在 2021/4/13 上午11:15, Xuan Zhuo 写道:
> virtnet_poll_tx() check the work done like other network card drivers.
>
> When work < budget, napi_poll() in dev.c will exit directly. And
> virtqueue_napi_complete() will be called to close napi. If closing napi
> fails or there is still data to be processed, virtqueue_napi_complete()
> will make napi schedule again, and no conflicts with the logic of
> napi_poll().
>
> When work == budget, virtnet_poll_tx() will return the var 'work', and
> the napi_poll() in dev.c will re-add napi to the queue.
>
> The purpose of this patch is to support xsk xmit in virtio_poll_tx for
> subsequent patch.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>


Acked-by: Jason Wang <jasowang@...hat.com>


> ---
>   drivers/net/virtio_net.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index f3752b254965..f52a25091322 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1529,6 +1529,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>   	struct virtnet_info *vi = sq->vq->vdev->priv;
>   	unsigned int index = vq2txq(sq->vq);
>   	struct netdev_queue *txq;
> +	int work_done = 0;
>   
>   	if (unlikely(is_xdp_raw_buffer_queue(vi, index))) {
>   		/* We don't need to enable cb for XDP */
> @@ -1541,12 +1542,13 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>   	free_old_xmit(sq, true);
>   	__netif_tx_unlock(txq);
>   
> -	virtqueue_napi_complete(napi, sq->vq, 0);
> +	if (work_done < budget)
> +		virtqueue_napi_complete(napi, sq->vq, 0);
>   
>   	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
>   		netif_tx_wake_queue(txq);
>   
> -	return 0;
> +	return work_done;
>   }
>   
>   static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)