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virtio_net: add support for Byte Queue Limits
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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: Jiri Pirko <jiri@nvidia.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20240618144456.1688998-1-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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@kuba-moo
Jiri Pirko authored and kuba-moo committed Jun 20, 2024
1 parent 2b0cd6b commit c8bd1f7
Showing 1 changed file with 57 additions and 24 deletions.
81 changes: 57 additions & 24 deletions drivers/net/virtio_net.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,8 @@ module_param(napi_tx, bool, 0644);
#define VIRTIO_XDP_TX BIT(0)
#define VIRTIO_XDP_REDIR BIT(1)

#define VIRTIO_XDP_FLAG BIT(0)
#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
Expand Down Expand Up @@ -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 {
Expand Down Expand Up @@ -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);

stats->bytes += skb->len;
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.
Expand Down Expand Up @@ -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);
}

Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand Down Expand Up @@ -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];
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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)) {
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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)
Expand All @@ -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)) {
Expand All @@ -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);
Expand Down

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