On Tue, Mar 21, 2023 at 06:03:14PM +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/
Link to v2:
https://lore.kernel.org/netdev/ea5725eb-6cb5-cf15-2938-34e335a442fa@xxxxxxxxxxxxxx/
Link to v3:
https://lore.kernel.org/netdev/f33ef593-982e-2b3f-0986-6d537a3aaf08@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.
v2 -> v3:
- Handle case when transport callback returns unexpected value which
is not equal to 'skb->len'. Break loop.
- Don't check for zero value of 'rest_len' before calling
'virtio_transport_put_credit()'. Decided to add this check directly
to 'virtio_transport_put_credit()' in separate patch.
v3 -> v4:
- Use WARN_ONCE() to handle case when transport callback returns
unexpected value.
- Remove useless 'ret = -EFAULT;' assignment for case above.
net/vmw_vsock/virtio_transport_common.c | 59 +++++++++++++++++++------
1 file changed, 45 insertions(+), 14 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 6564192e7f20..a300f25749ea 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 +224,51 @@ 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;
nit: this initialization seems superfluous since `ret` is
overwritten later ...
+ 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);
+ virtio_transport_inc_tx_pkt(vvs, skb);
- return t_ops->send_pkt(skb);
+ ret = t_ops->send_pkt(skb);
... here.
+
nit: we can remove this extra line
+ if (ret < 0)
+ break;
+
+ /* Both virtio and vhost 'send_pkt()' returns 'skb_len',
+ * but for reliability use 'ret' instead of 'skb_len'.
+ * Also if partial send happens (e.g. 'ret' != 'skb_len')
+ * somehow, we break this loop, but account such returned
+ * value in 'virtio_transport_put_credit()'.
+ */
+ rest_len -= ret;
+
+ if (WARN_ONCE(ret != skb_len,
+ "'send_pkt()' returns %i, but %zu expected\n",
+ ret, skb_len))
+ break;
+ } while (rest_len);
+
+ virtio_transport_put_credit(vvs, rest_len);
+
+ /* Return number of bytes, if any data has been sent. */
+ if (rest_len != pkt_len)
+ ret = pkt_len - rest_len;
+
+ return ret;
}
static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,
-- 2.25.1
The patch LGTM:
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Anyway, feel free to include in the same series or as separate patch
also the changes to avoid useless lock in virtio_transport_put_credit()
and virtio_transport_get_credit().
I would include it in this series, because before these changes, we
used to call virtio_transport_put_credit() only in the error path,
while now we always call it, even when rest_len is 0.
Thanks,
Stefano
