netdev - Re: [PATCH 29/33] virtio_net: xsk: tx: support tx

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Date:   Fri, 3 Feb 2023 09:39:25 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
CC:     <netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>,
        "Eric Dumazet" <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        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>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Menglong Dong <imagedong@...cent.com>,
        "Kuniyuki Iwashima" <kuniyu@...zon.com>,
        Petr Machata <petrm@...dia.com>,
        <virtualization@...ts.linux-foundation.org>, <bpf@...r.kernel.org>
Subject: Re: [PATCH 29/33] virtio_net: xsk: tx: support tx

On Thu, Feb 02, 2023 at 07:00:54PM +0800, Xuan Zhuo wrote:
> The driver's tx napi is very important for XSK. It is responsible for
> obtaining data from the XSK queue and sending it out.
> 
> At the beginning, we need to trigger tx napi.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio/main.c |  12 +++-
>  drivers/net/virtio/xsk.c  | 146 ++++++++++++++++++++++++++++++++++++++
>  drivers/net/virtio/xsk.h  |   2 +
>  3 files changed, 159 insertions(+), 1 deletion(-)
> 

(...)

> +static int virtnet_xsk_xmit_batch(struct send_queue *sq,
> +				  struct xsk_buff_pool *pool,
> +				  unsigned int budget,
> +				  struct virtnet_sq_stats *stats)
> +{
> +	int ret = XSK_XMIT_NO_BUDGET;
> +	struct xdp_desc desc;
> +	int err, packet = 0;
> +
> +	while (budget-- > 0) {
> +		if (sq->vq->num_free < 2) {
> +			__free_old_xmit(sq, true, stats);
> +			if (sq->vq->num_free < 2) {
> +				ret = XSK_XMIT_DEV_BUSY;
> +				break;
> +			}
> +		}
> +
> +		if (!xsk_tx_peek_desc(pool, &desc)) {

anything that stopped from using xsk_tx_peek_release_desc_batch() ?

> +			ret = XSK_XMIT_DONE;
> +			break;
> +		}
> +
> +		err = virtnet_xsk_xmit_one(sq, pool, &desc);
> +		if (unlikely(err)) {
> +			ret = XSK_XMIT_DEV_BUSY;
> +			break;
> +		}
> +
> +		++packet;
> +
> +		if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
> +			++stats->kicks;
> +	}
> +
> +	if (packet) {
> +		stats->xdp_tx += packet;
> +
> +		xsk_tx_release(pool);
> +	}
> +
> +	return ret;
> +}
> +
> +bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
> +		      int budget)
> +{
> +	struct virtnet_sq_stats stats = {};
> +	bool busy;
> +	int ret;
> +
> +	__free_old_xmit(sq, true, &stats);
> +
> +	if (xsk_uses_need_wakeup(pool))
> +		xsk_set_tx_need_wakeup(pool);
> +
> +	ret = virtnet_xsk_xmit_batch(sq, pool, budget, &stats);
> +	switch (ret) {
> +	case XSK_XMIT_DONE:
> +		/* xsk tx qeueu has been consumed done. should complete napi. */
> +		busy = false;
> +		break;
> +
> +	case XSK_XMIT_NO_BUDGET:
> +		/* reach the budget limit. should let napi run again. */
> +		busy = true;
> +		break;
> +
> +	case XSK_XMIT_DEV_BUSY:
> +		/* sq vring is full, should complete napi. wait for tx napi been
> +		 * triggered by interrupt.
> +		 */
> +		busy = false;
> +		break;
> +	}
> +
> +	virtnet_xsk_check_queue(sq);
> +
> +	u64_stats_update_begin(&sq->stats.syncp);
> +	sq->stats.packets += stats.packets;
> +	sq->stats.bytes += stats.bytes;
> +	sq->stats.kicks += stats.kicks;
> +	sq->stats.xdp_tx += stats.xdp_tx;
> +	u64_stats_update_end(&sq->stats.syncp);
> +
> +	return busy;
> +}
> +
>  static int virtnet_rq_bind_xsk_pool(struct virtnet_info *vi, struct receive_queue *rq,
>  				    struct xsk_buff_pool *pool, struct net_device *dev)
>  {
> diff --git a/drivers/net/virtio/xsk.h b/drivers/net/virtio/xsk.h
> index ad684c812091..15f1540a5803 100644
> --- a/drivers/net/virtio/xsk.h
> +++ b/drivers/net/virtio/xsk.h
> @@ -20,4 +20,6 @@ static inline u32 ptr_to_xsk(void *ptr)
>  }
>  
>  int virtnet_xsk_pool_setup(struct net_device *dev, struct netdev_bpf *xdp);
> +bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
> +		      int budget);
>  #endif
> -- 
> 2.32.0.3.g01195cf9f
>