On 2020/12/9 下午9:27, wangyunjian wrote:
-----Original Message-----
From: Michael S. Tsirkin [mailto:mst@xxxxxxxxxx]
Sent: Wednesday, December 9, 2020 8:50 PM
To: wangyunjian <wangyunjian@xxxxxxxxxx>
Cc: jasowang@xxxxxxxxxx; virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx;
netdev@xxxxxxxxxxxxxxx; Lilijun (Jerry) <jerry.lilijun@xxxxxxxxxx>;
chenchanghu <chenchanghu@xxxxxxxxxx>; xudingke <xudingke@xxxxxxxxxx>
Subject: Re: [PATCH net] vhost_net: fix high cpu load when sendmsg fails
On Wed, Dec 09, 2020 at 07:48:24PM +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.
Signed-off-by: Yunjian Wang <wangyunjian@xxxxxxxxxx>
---
drivers/vhost/net.c | 24 +++++-------------------
1 file changed, 5 insertions(+), 19 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index
531a00d703cd..ac950b1120f5 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -829,14 +829,8 @@ static void handle_tx_copy(struct vhost_net *net,
struct socket *sock)
/* TODO: Check specific error and bomb out unless ENOBUFS? */
err = sock->ops->sendmsg(sock, &msg, len);
- if (unlikely(err < 0)) {
- 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);
+ if (unlikely(err < 0 || 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;
One of the reasons for sendmsg to fail is ENOBUFS.
In that case for sure we don't want to drop packet.
Now the function tap_sendmsg()/tun_sendmsg() don't return ENOBUFS.
I think not, it can happen if we exceeds sndbuf. E.g see tun_alloc_skb().
Thanks
There could be other transient errors.
Which error did you encounter, specifically?
Currently a guest vm send a skb which length is more than 64k.
If virtio hdr is wrong, the problem will also be triggered.
Thanks
@@ -925,19 +919,11 @@ static void handle_tx_zerocopy(struct vhost_net
*net, struct socket *sock)
/* TODO: Check specific error and bomb out unless ENOBUFS? */
err = sock->ops->sendmsg(sock, &msg, len);
- if (unlikely(err < 0)) {
- if (zcopy_used) {
+ if (unlikely(err < 0 || err != len)) {
+ if (zcopy_used && err < 0)
vhost_net_ubuf_put(ubufs);
- nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
- % UIO_MAXIOV;
- }
- vhost_discard_vq_desc(vq, 1);
- vhost_net_enable_vq(net, vq);
- break;
+ vq_err(vq, "Fail to sending packets err : %d, len : %zd\n", err,
+len);
}
- if (err != len)
- pr_debug("Truncated TX packet: "
- " len %d != %zd\n", err, len);
if (!zcopy_used)
vhost_add_used_and_signal(&net->dev, vq, head, 0);
else
--
2.23.0
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