On Wed, Dec 16, 2020 at 04:20:37PM +0800, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@xxxxxxxxxx>
>
> Currently we break the loop and wake up the vhost_worker when
> sendmsg fails. When the worker wakes up again, we'll meet the
> same error. This will cause high CPU load. To fix this issue,
> we can skip this description by ignoring the error. When we
> exceeds sndbuf, the return value of sendmsg is -EAGAIN. In
> the case we don't skip the description and don't drop packet.
Question: with this patch, what happens if sendmsg is interrupted by a signal?
>
> Signed-off-by: Yunjian Wang <wangyunjian@xxxxxxxxxx>
> ---
> drivers/vhost/net.c | 21 +++++++++------------
> 1 file changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index c8784dfafdd7..3d33f3183abe 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -827,16 +827,13 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
> msg.msg_flags &= ~MSG_MORE;
> }
>
> - /* TODO: Check specific error and bomb out unless ENOBUFS? */
> err = sock->ops->sendmsg(sock, &msg, len);
> - if (unlikely(err < 0)) {
> + if (unlikely(err == -EAGAIN)) {
> vhost_discard_vq_desc(vq, 1);
> vhost_net_enable_vq(net, vq);
> break;
> - }
> - if (err != len)
> - pr_debug("Truncated TX packet: len %d != %zd\n",
> - err, len);
> + } else if (unlikely(err != len))
> + vq_err(vq, "Fail to sending packets err : %d, len : %zd\n", err, len);
> done:
> vq->heads[nvq->done_idx].id = cpu_to_vhost32(vq, head);
> vq->heads[nvq->done_idx].len = 0;
> @@ -922,7 +919,6 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
> msg.msg_flags &= ~MSG_MORE;
> }
>
> - /* TODO: Check specific error and bomb out unless ENOBUFS? */
> err = sock->ops->sendmsg(sock, &msg, len);
> if (unlikely(err < 0)) {
> if (zcopy_used) {
> @@ -931,13 +927,14 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
> nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
> % UIO_MAXIOV;
> }
> - vhost_discard_vq_desc(vq, 1);
> - vhost_net_enable_vq(net, vq);
> - break;
> + if (err == -EAGAIN) {
> + vhost_discard_vq_desc(vq, 1);
> + vhost_net_enable_vq(net, vq);
> + break;
> + }
> }
> if (err != len)
> - pr_debug("Truncated TX packet: "
> - " len %d != %zd\n", err, len);
> + vq_err(vq, "Fail to sending packets err : %d, len : %zd\n", err, len);
I'd rather make the pr_debug -> vq_err a separate change, with proper
commit log describing motivation.
> if (!zcopy_used)
> vhost_add_used_and_signal(&net->dev, vq, head, 0);
> else
> --
> 2.23.0
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