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Date: Tue, 7 May 2024 12:11:59 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Paolo Abeni <pabeni@...hat.com>,
Luigi Leonardi <luigi.leonardi@...look.com>
Cc: mst@...hat.com, xuanzhuo@...ux.alibaba.com,
virtualization@...ts.linux.dev, netdev@...r.kernel.org, kuba@...nel.org, stefanha@...hat.com,
davem@...emloft.net, edumazet@...gle.com, kvm@...r.kernel.org, jasowang@...hat.com
Subject: Re: [PATCH net-next v2 2/3] vsock/virtio: add SIOCOUTQ support for
all virtio based transports
On Thu, Apr 11, 2024 at 09:09:49AM GMT, Paolo Abeni wrote:
>On Mon, 2024-04-08 at 15:37 +0200, Luigi Leonardi wrote:
>> This patch introduce support for stream_bytes_unsent and
>> seqpacket_bytes_unsent ioctl for virtio_transport, vhost_vsock
>> and vsock_loopback.
>>
>> For all transports the unsent bytes counter is incremented
>> in virtio_transport_send_pkt_info.
>>
>> In the virtio_transport (G2H) the counter is decremented each time the host
>> notifies the guest that it consumed the skbuffs.
>> In vhost-vsock (H2G) the counter is decremented after the skbuff is queued
>> in the virtqueue.
>> In vsock_loopback the counter is decremented after the skbuff is
>> dequeued.
>>
>> Signed-off-by: Luigi Leonardi <luigi.leonardi@...look.com>
>
>I think this deserve an explicit ack from Stefano, and Stefano can't
>review patches in the next few weeks. If it's not urgent this will have
>to wait a bit.
>
>> ---
>> drivers/vhost/vsock.c | 4 ++-
>> include/linux/virtio_vsock.h | 7 ++++++
>> net/vmw_vsock/virtio_transport.c | 4 ++-
>> net/vmw_vsock/virtio_transport_common.c | 33 +++++++++++++++++++++++++
>> net/vmw_vsock/vsock_loopback.c | 7 ++++++
>> 5 files changed, 53 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>> index ec20ecff85c7..dba8b3ea37bf 100644
>> --- a/drivers/vhost/vsock.c
>> +++ b/drivers/vhost/vsock.c
>> @@ -244,7 +244,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
>> restart_tx = true;
>> }
>>
>> - consume_skb(skb);
>> + virtio_transport_consume_skb_sent(skb, true);
>> }
>> } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
>> if (added)
>> @@ -451,6 +451,8 @@ static struct virtio_transport vhost_transport = {
>> .notify_buffer_size = virtio_transport_notify_buffer_size,
>> .notify_set_rcvlowat = virtio_transport_notify_set_rcvlowat,
>>
>> + .unsent_bytes = virtio_transport_bytes_unsent,
>> +
>> .read_skb = virtio_transport_read_skb,
>> },
>>
>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> index c82089dee0c8..dbb22d45d203 100644
>> --- a/include/linux/virtio_vsock.h
>> +++ b/include/linux/virtio_vsock.h
>> @@ -134,6 +134,8 @@ struct virtio_vsock_sock {
>> u32 peer_fwd_cnt;
>> u32 peer_buf_alloc;
>>
>> + atomic_t bytes_unsent;
>
>This will add 2 atomic operations per packet, possibly on contended
>cachelines. Have you considered leveraging the existing transport-level
>lock to protect the counter updates?
Good point!
Maybe we can handle it together with `tx_cnt` in
virtio_transport_get_credit()/virtio_transport_put_credit().
Eventually these are called exactly to count the payload we are sending
(`tx_cnt` is a counter that only grows, virtio_transport_put_credit() is
called only to return unused credit, so we can't use it directly but
always need a new variable like `bytes_unsent`).
I mean something like this (untested at all):
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index dbb22d45d203..713197c16b7f 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -133,8 +133,7 @@ struct virtio_vsock_sock {
u32 tx_cnt;
u32 peer_fwd_cnt;
u32 peer_buf_alloc;
-
- atomic_t bytes_unsent;
+ u32 bytes_unsent;
/* Protected by rx_lock */
u32 fwd_cnt;
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 82a31a13dc32..b1a51db616cf 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -419,13 +419,6 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
*/
rest_len -= ret;
- /* Avoid to perform an atomic_add on 0 bytes.
- * This is equivalent to check on VIRTIO_VSOCK_OP_RW
- * as is the only packet type with payload.
- */
- if (ret)
- atomic_add(ret, &vvs->bytes_unsent);
-
if (WARN_ONCE(ret != skb_len,
"'send_pkt()' returns %i, but %zu expected\n",
ret, skb_len))
@@ -479,7 +472,10 @@ void virtio_transport_consume_skb_sent(struct sk_buff *skb, bool consume)
struct virtio_vsock_sock *vvs;
vvs = vs->trans;
- atomic_sub(skb->len, &vvs->bytes_unsent);
+
+ spin_lock_bh(&vvs->tx_lock);
+ vvs->bytes_unsent -= skb->len;
+ spin_unlock_bh(&vvs->tx_lock);
}
if (consume)
@@ -499,6 +495,7 @@ u32 virtio_transport_get_credit(struct virtio_vsock_sock *vvs, u32 credit)
if (ret > credit)
ret = credit;
vvs->tx_cnt += ret;
+ vvs->bytes_unsent += ret;
spin_unlock_bh(&vvs->tx_lock);
return ret;
@@ -512,6 +509,7 @@ void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit)
spin_lock_bh(&vvs->tx_lock);
vvs->tx_cnt -= credit;
+ vvs->bytes_unsent -= ret;
spin_unlock_bh(&vvs->tx_lock);
}
EXPORT_SYMBOL_GPL(virtio_transport_put_credit);
@@ -915,7 +913,6 @@ int virtio_transport_do_socket_init(struct vsock_sock *vsk,
vsk->buffer_size = VIRTIO_VSOCK_MAX_BUF_SIZE;
vvs->buf_alloc = vsk->buffer_size;
- atomic_set(&vvs->bytes_unsent, 0);
spin_lock_init(&vvs->rx_lock);
spin_lock_init(&vvs->tx_lock);
@@ -1118,8 +1115,13 @@ EXPORT_SYMBOL_GPL(virtio_transport_destruct);
int virtio_transport_bytes_unsent(struct vsock_sock *vsk)
{
struct virtio_vsock_sock *vvs = vsk->trans;
+ int ret;
- return atomic_read(&vvs->bytes_unsent);
+ spin_lock_bh(&vvs->tx_lock);
+ ret = vvs->bytes_unsent;
+ spin_unlock_bh(&vvs->tx_lock);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(virtio_transport_bytes_unsent);
WDYT?
Should virtio_transport_bytes_unsent() returns size_t?
Thanks,
Stefano
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