On 21.03.2023 11:40, Stefano Garzarella wrote: > On Tue, Mar 21, 2023 at 12:31:48AM +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/ >> >> 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. >> >> 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..e0b2c6ecbe22 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; >> + 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); >> + ret = t_ops->send_pkt(skb); >> >> - return t_ops->send_pkt(skb); >> + 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 (ret != skb_len) { >> + ret = -EFAULT; > > Okay, but `ret` will be overwritten by the check we have before the > return ... > Yes, you're right, this assignment has no effect, since 'rest_len' is already changed and ret will be changed. I'll fix it. Thanks, Arseniy >> + 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; > > ... here. > > Since we don't expect this condition for now, perhaps we can avoid > setting ret with -EFAULT, but we can add a WARN_ONCE (interrupting the > loop as you did here). > > This way we return the partial length as we did before. > > Thanks, > Stefano > >> + >> + return ret; >> } >> >> static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, >> -- >> 2.25.1 >> >
