On Mon, Mar 20, 2023 at 09:02:19PM +0300, Arseniy Krasnov wrote:
On 20.03.2023 17:29, Stefano Garzarella wrote:
On Sun, Mar 19, 2023 at 09:46:10PM +0300, Arseniy Krasnov wrote:
This adds small optimization for tx path: instead of allocating single
skbuff on every call to transport, allocate multiple skbuff's until
credit space allows, thus trying to send as much as possible data without
return to af_vsock.c.
Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
---
Link to v1:
https://lore.kernel.org/netdev/2c52aa26-8181-d37a-bccd-a86bd3cbc6e1@xxxxxxxxxxxxxx/
Changelog:
v1 -> v2:
- If sent something, return number of bytes sent (even in
case of error). Return error only if failed to sent first
skbuff.
net/vmw_vsock/virtio_transport_common.c | 53 ++++++++++++++++++-------
1 file changed, 39 insertions(+), 14 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 6564192e7f20..3fdf1433ec28 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -196,7 +196,8 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
const struct virtio_transport *t_ops;
struct virtio_vsock_sock *vvs;
u32 pkt_len = info->pkt_len;
- struct sk_buff *skb;
+ u32 rest_len;
+ int ret;
info->type = virtio_transport_get_type(sk_vsock(vsk));
@@ -216,10 +217,6 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
vvs = vsk->trans;
- /* we can send less than pkt_len bytes */
- if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
- pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
-
/* virtio_transport_get_credit might return less than pkt_len credit */
pkt_len = virtio_transport_get_credit(vvs, pkt_len);
@@ -227,17 +224,45 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
return pkt_len;
- skb = virtio_transport_alloc_skb(info, pkt_len,
- src_cid, src_port,
- dst_cid, dst_port);
- if (!skb) {
- virtio_transport_put_credit(vvs, pkt_len);
- return -ENOMEM;
- }
+ ret = 0;
+ rest_len = pkt_len;
+
+ do {
+ struct sk_buff *skb;
+ size_t skb_len;
+
+ skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len);
+
+ skb = virtio_transport_alloc_skb(info, skb_len,
+ src_cid, src_port,
+ dst_cid, dst_port);
+ if (!skb) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ virtio_transport_inc_tx_pkt(vvs, skb);
+
+ ret = t_ops->send_pkt(skb);
+
+ if (ret < 0)
+ break;
- virtio_transport_inc_tx_pkt(vvs, skb);
+ rest_len -= skb_len;
t_ops->send_pkt() is returning the number of bytes sent. Current
implementations always return `skb_len`, so there should be no problem,
but it would be better to put a comment here, or we should handle the
case where ret != skb_len to avoid future issues.
Hello, thanks for review!
I see. I think i'll handle such partial sends (ret != skb_len) as error, as
it is the only thing to do - we remove 'skb_len' from user's buffer, but
'send_pkt()' returns another value, so it will be strange for me to continue
this tx loop as everything is ok. Something like this:
+
+ if (ret < 0)
+ break;
+
+ if (ret != skb_len) {
+ ret = -EFAULT;//or may be -EIO
+ break;
+ }
Good for me.
+ } while (rest_len);
- return t_ops->send_pkt(skb);
+ /* Don't call this function with zero as argument:
+ * it tries to acquire spinlock and such argument
+ * makes this call useless.
Good point, can we do the same also for virtio_transport_get_credit()?
(Maybe in a separate patch)
I'm thinking if may be better to do it directly inside the functions,
but I don't have a strong opinion on that since we only call them here.
I think in this patch i can call 'virtio_transport_put_credit()' without if, but
i'll prepare separate patch which adds zero argument check to this function.
Yep, I agree.
As i see, the only function suitable for such 'if' condition is
'virtio_transport_put_credit()'.
Why not even for virtio_transport_get_credit() ?
When we send packets without payload (e.g. VIRTIO_VSOCK_OP_REQUEST,
VIRTIO_VSOCK_OP_SHUTDOWN) we call virtio_transport_get_credit()
with `credit` parameter equal to 0, then we acquire the spinlock but
in the end we do nothing.
Anyway - for future use this check won't be bad.
Yep, these are minor improvements ;-)
Thanks,
Stefano
