Re: [PATCH 6.10 259/809] virtio_net: add support for Byte Queue Limits

On Tue, Jul 30, 2024 at 05:42:15PM +0200, Greg Kroah-Hartman wrote:

6.10-stable review patch. If anyone has any objections, please let me know.

Wow.

It's clearly a feature, not a bugfix. And a risky one, at that.

Applies to any stable tree.

---

From: Jiri Pirko jiri@nvidia.com

[ Upstream commit c8bd1f7f3e61fc6c562c806045f3ccd2cc819c01 ]

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 Stable-dep-of: f8321fa75102 ("virtio_net: Fix napi_skb_cache_put warning") Signed-off-by: Sasha Levin sashal@kernel.org

---

drivers/net/virtio_net.c | 81 ++++++++++++++++++++++++++++------------ 1 file changed, 57 insertions(+), 24 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index ea10db9a09fa2..b1f8b720733e5 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -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

@@ -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);

• 	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. @@ -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]; @@ -2331,7 +2359,7 @@ 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) { @@ -2430,6 +2458,7 @@ 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; @@ -2489,7 +2518,7 @@ 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)) { @@ -2523,7 +2552,7 @@ 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; @@ -2567,7 +2596,8 @@ 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) @@ -2577,24 +2607,25 @@ 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)) { @@ -2616,7 +2647,9 @@ 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);

-- 2.43.0