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Subject[PATCH RFC 1/4] vsock/virtio: reduce credit update messages
Date
In order to reduce the number of credit update messages,
we send them only when the space available seen by the
transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
include/linux/virtio_vsock.h | 1 +
net/vmw_vsock/virtio_transport_common.c | 14 +++++++++++---
2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index e223e2632edd..6d7a22cc20bf 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -37,6 +37,7 @@ struct virtio_vsock_sock {
u32 tx_cnt;
u32 buf_alloc;
u32 peer_fwd_cnt;
+ u32 last_fwd_cnt;
u32 peer_buf_alloc;

/* Protected by rx_lock */
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 602715fc9a75..f32301d823f5 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -206,6 +206,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
{
spin_lock_bh(&vvs->tx_lock);
+ vvs->last_fwd_cnt = vvs->fwd_cnt;
pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
spin_unlock_bh(&vvs->tx_lock);
@@ -256,6 +257,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
struct virtio_vsock_sock *vvs = vsk->trans;
struct virtio_vsock_pkt *pkt;
size_t bytes, total = 0;
+ s64 free_space;
int err = -EFAULT;

spin_lock_bh(&vvs->rx_lock);
@@ -288,9 +290,15 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
}
spin_unlock_bh(&vvs->rx_lock);

- /* Send a credit pkt to peer */
- virtio_transport_send_credit_update(vsk, VIRTIO_VSOCK_TYPE_STREAM,
- NULL);
+ /* We send a credit update only when the space available seen
+ * by the transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE
+ */
+ free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt);
+ if (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
+ virtio_transport_send_credit_update(vsk,
+ VIRTIO_VSOCK_TYPE_STREAM,
+ NULL);
+ }

return total;

--
2.20.1
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