Merge branch 'vsock-virtio' into main

Luigi Leonardi says:

====================
vsock: avoid queuing on intermediate queue if possible

This series introduces an optimization for vsock/virtio to reduce latency
and increase the throughput: When the guest sends a packet to the host,
and the intermediate queue (send_pkt_queue) is empty, if there is enough
space, the packet is put directly in the virtqueue.

v3->v4
While running experiments on fio with 64B payload, I realized that there
was a mistake in my fio configuration, so I re-ran all the experiments
and now the latency numbers are indeed lower with the patch applied.
I also noticed that I was kicking the host without the lock.

- Fixed a configuration mistake on fio and re-ran all experiments.
- Fio latency measurement using 64B payload.
- virtio_transport_send_skb_fast_path sends kick with the tx_lock acquired
- Addressed all minor style changes requested by maintainer.
- Rebased on latest net-next
- Link to v3: https://lore.kernel.org/r/20240711-pinna-v3-0-697d4164fe80@outlook.com

v2->v3
- Performed more experiments using iperf3 using multiple streams
- Handling of reply packets removed from virtio_transport_send_skb,
  as is needed just by the worker.
- Removed atomic_inc/atomic_sub when queuing directly to the vq.
- Introduced virtio_transport_send_skb_fast_path that handles the
  steps for sending on the vq.
- Fixed a missing mutex_unlock in error path.
- Changed authorship of the second commit
- Rebased on latest net-next

v1->v2
In this v2 I replaced a mutex_lock with a mutex_trylock because it was
insidea RCU critical section. I also added a check on tx_run, so if the
module is being removed the packet is not queued. I'd like to thank Stefano
for reporting the tx_run issue.

Applied all Stefano's suggestions:
    - Minor code style changes
    - Minor commit text rewrite
Performed more experiments:
     - Check if all the packets go directly to the vq (Matias' suggestion)
     - Used iperf3 to see if there is any improvement in overall throughput
      from guest to host
     - Pinned the vhost process to a pCPU.
     - Run fio using 512B payload
Rebased on latest net-next
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index c82089dee0c8..0387d64e2c66 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -133,6 +133,7 @@ struct virtio_vsock_sock {
 	u32 tx_cnt;
 	u32 peer_fwd_cnt;
 	u32 peer_buf_alloc;
+	size_t bytes_unsent;
 
 	/* Protected by rx_lock */
 	u32 fwd_cnt;
@@ -193,6 +194,11 @@ s64 virtio_transport_stream_has_data(struct vsock_sock *vsk);
 s64 virtio_transport_stream_has_space(struct vsock_sock *vsk);
 u32 virtio_transport_seqpacket_has_data(struct vsock_sock *vsk);
 
+ssize_t virtio_transport_unsent_bytes(struct vsock_sock *vsk);
+
+void virtio_transport_consume_skb_sent(struct sk_buff *skb,
+				       bool consume);
+
 int virtio_transport_do_socket_init(struct vsock_sock *vsk,
 				 struct vsock_sock *psk);
 int
diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 535701efc1e5..fc504d2da3d0 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -169,6 +169,9 @@ struct vsock_transport {
 	void (*notify_buffer_size)(struct vsock_sock *, u64 *);
 	int (*notify_set_rcvlowat)(struct vsock_sock *vsk, int val);
 
+	/* SIOCOUTQ ioctl */
+	ssize_t (*unsent_bytes)(struct vsock_sock *vsk);
+
 	/* Shutdown. */
 	int (*shutdown)(struct vsock_sock *, int);