Commit c8bd1f7f authored by Jiri Pirko's avatar Jiri Pirko Committed by Jakub Kicinski
Browse files

virtio_net: add support for Byte Queue Limits 



Add support for Byte Queue Limits (BQL).

Tested on qemu emulated virtio_net device with 1, 2 and 4 queues.
Tested with fq_codel and pfifo_fast. Super netperf with 50 threads is
running in background. Netperf TCP_RR results:

NOBQL FQC 1q:  159.56  159.33  158.50  154.31    agv: 157.925
NOBQL FQC 2q:  184.64  184.96  174.73  174.15    agv: 179.62
NOBQL FQC 4q:  994.46  441.96  416.50  499.56    agv: 588.12
NOBQL PFF 1q:  148.68  148.92  145.95  149.48    agv: 148.2575
NOBQL PFF 2q:  171.86  171.20  170.42  169.42    agv: 170.725
NOBQL PFF 4q: 1505.23 1137.23 2488.70 3507.99    agv: 2159.7875
  BQL FQC 1q: 1332.80 1297.97 1351.41 1147.57    agv: 1282.4375
  BQL FQC 2q:  768.30  817.72  864.43  974.40    agv: 856.2125
  BQL FQC 4q:  945.66  942.68  878.51  822.82    agv: 897.4175
  BQL PFF 1q:  149.69  151.49  149.40  147.47    agv: 149.5125
  BQL PFF 2q: 2059.32  798.74 1844.12  381.80    agv: 1270.995
  BQL PFF 4q: 1871.98 4420.02 4916.59 13268.16   agv: 6119.1875

Signed-off-by: default avatarJiri Pirko <jiri@nvidia.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20240618144456.1688998-1-jiri@resnulli.us


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 2b0cd6b7

drivers/net/virtio_net.c

+57 −24
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ module_param(napi_tx, bool, 0644); 
#define VIRTIO_XDP_REDIR	BIT(1)



#define VIRTIO_XDP_FLAG		BIT(0)

#define VIRTIO_ORPHAN_FLAG	BIT(1)



/* RX packet size EWMA. The average packet size is used to determine the packet

 * buffer size when refilling RX rings. As the entire RX ring may be refilled
@@ -85,6 +86,8 @@ struct virtnet_stat_desc { 
struct virtnet_sq_free_stats {

	u64 packets;

	u64 bytes;

	u64 napi_packets;

	u64 napi_bytes;

};



struct virtnet_sq_stats {
@@ -506,29 +509,50 @@ static struct xdp_frame *ptr_to_xdp(void *ptr) 
	return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);

}



static void __free_old_xmit(struct send_queue *sq, bool in_napi,

			    struct virtnet_sq_free_stats *stats)

static bool is_orphan_skb(void *ptr)

{

	return (unsigned long)ptr & VIRTIO_ORPHAN_FLAG;

}



static void *skb_to_ptr(struct sk_buff *skb, bool orphan)

{

	return (void *)((unsigned long)skb | (orphan ? VIRTIO_ORPHAN_FLAG : 0));

}



static struct sk_buff *ptr_to_skb(void *ptr)

{

	return (struct sk_buff *)((unsigned long)ptr & ~VIRTIO_ORPHAN_FLAG);

}



static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,

			    bool in_napi, struct virtnet_sq_free_stats *stats)

{

	unsigned int len;

	void *ptr;



	while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {

		++stats->packets;



		if (!is_xdp_frame(ptr)) {

			struct sk_buff *skb = ptr;

			struct sk_buff *skb = ptr_to_skb(ptr);



			pr_debug("Sent skb %p\n", skb);



			if (is_orphan_skb(ptr)) {

				stats->packets++;

				stats->bytes += skb->len;

			} else {

				stats->napi_packets++;

				stats->napi_bytes += skb->len;

			}

			napi_consume_skb(skb, in_napi);

		} else {

			struct xdp_frame *frame = ptr_to_xdp(ptr);



			stats->packets++;

			stats->bytes += xdp_get_frame_len(frame);

			xdp_return_frame(frame);

		}

	}

	netdev_tx_completed_queue(txq, stats->napi_packets, stats->napi_bytes);

}



/* Converting between virtqueue no. and kernel tx/rx queue no.
@@ -955,21 +979,22 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf) 
	virtnet_rq_free_buf(vi, rq, buf);

}



static void free_old_xmit(struct send_queue *sq, bool in_napi)

static void free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,

			  bool in_napi)

{

	struct virtnet_sq_free_stats stats = {0};



	__free_old_xmit(sq, in_napi, &stats);

	__free_old_xmit(sq, txq, in_napi, &stats);



	/* Avoid overhead when no packets have been processed

	 * happens when called speculatively from start_xmit.

	 */

	if (!stats.packets)

	if (!stats.packets && !stats.napi_packets)

		return;



	u64_stats_update_begin(&sq->stats.syncp);

	u64_stats_add(&sq->stats.bytes, stats.bytes);

	u64_stats_add(&sq->stats.packets, stats.packets);

	u64_stats_add(&sq->stats.bytes, stats.bytes + stats.napi_bytes);

	u64_stats_add(&sq->stats.packets, stats.packets + stats.napi_packets);

	u64_stats_update_end(&sq->stats.syncp);

}
@@ -1003,7 +1028,9 @@ static void check_sq_full_and_disable(struct virtnet_info *vi, 
	 * early means 16 slots are typically wasted.

	 */

	if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {

		netif_stop_subqueue(dev, qnum);

		struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);



		netif_tx_stop_queue(txq);

		u64_stats_update_begin(&sq->stats.syncp);

		u64_stats_inc(&sq->stats.stop);

		u64_stats_update_end(&sq->stats.syncp);
@@ -1012,7 +1039,7 @@ static void check_sq_full_and_disable(struct virtnet_info *vi, 
				virtqueue_napi_schedule(&sq->napi, sq->vq);

		} else if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {

			/* More just got used, free them then recheck. */

			free_old_xmit(sq, false);

			free_old_xmit(sq, txq, false);

			if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) {

				netif_start_subqueue(dev, qnum);

				u64_stats_update_begin(&sq->stats.syncp);
@@ -1138,7 +1165,8 @@ static int virtnet_xdp_xmit(struct net_device *dev, 
	}



	/* Free up any pending old buffers before queueing new ones. */

	__free_old_xmit(sq, false, &stats);

	__free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq),

			false, &stats);



	for (i = 0; i < n; i++) {

		struct xdp_frame *xdpf = frames[i];
@@ -2313,7 +2341,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) 


		do {

			virtqueue_disable_cb(sq->vq);

			free_old_xmit(sq, true);

			free_old_xmit(sq, txq, true);

		} while (unlikely(!virtqueue_enable_cb_delayed(sq->vq)));



		if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {
@@ -2412,6 +2440,7 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index) 
		goto err_xdp_reg_mem_model;



	virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);

	netdev_tx_reset_queue(netdev_get_tx_queue(vi->dev, qp_index));

	virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi);



	return 0;
@@ -2471,7 +2500,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) 
	txq = netdev_get_tx_queue(vi->dev, index);

	__netif_tx_lock(txq, raw_smp_processor_id());

	virtqueue_disable_cb(sq->vq);

	free_old_xmit(sq, true);

	free_old_xmit(sq, txq, true);



	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {

		if (netif_tx_queue_stopped(txq)) {
@@ -2505,7 +2534,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) 
	return 0;

}



static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)

static int xmit_skb(struct send_queue *sq, struct sk_buff *skb, bool orphan)

{

	struct virtio_net_hdr_mrg_rxbuf *hdr;

	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
@@ -2549,7 +2578,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) 
			return num_sg;

		num_sg++;

	}

	return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);

	return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg,

				    skb_to_ptr(skb, orphan), GFP_ATOMIC);

}



static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
@@ -2559,24 +2589,25 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) 
	struct send_queue *sq = &vi->sq[qnum];

	int err;

	struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);

	bool kick = !netdev_xmit_more();

	bool xmit_more = netdev_xmit_more();

	bool use_napi = sq->napi.weight;

	bool kick;



	/* Free up any pending old buffers before queueing new ones. */

	do {

		if (use_napi)

			virtqueue_disable_cb(sq->vq);



		free_old_xmit(sq, false);

		free_old_xmit(sq, txq, false);



	} while (use_napi && kick &&

	} while (use_napi && !xmit_more &&

	       unlikely(!virtqueue_enable_cb_delayed(sq->vq)));



	/* timestamp packet in software */

	skb_tx_timestamp(skb);



	/* Try to transmit */

	err = xmit_skb(sq, skb);

	err = xmit_skb(sq, skb, !use_napi);



	/* This should not happen! */

	if (unlikely(err)) {
@@ -2598,7 +2629,9 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) 


	check_sq_full_and_disable(vi, dev, sq);



	if (kick || netif_xmit_stopped(txq)) {

	kick = use_napi ? __netdev_tx_sent_queue(txq, skb->len, xmit_more) :

			  !xmit_more || netif_xmit_stopped(txq);

	if (kick) {

		if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) {

			u64_stats_update_begin(&sq->stats.syncp);

			u64_stats_inc(&sq->stats.kicks);