@@ -197,8 +197,18 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status)
{
struct vhost_ubuf_ref *ubufs = ubuf->ctx;
struct vhost_virtqueue *vq = ubufs->vq;
-
- vhost_poll_queue(&vq->poll);
+ int cnt = atomic_read(&ubufs->kref.refcount);
+
+ /*
+ * Trigger polling thread if guest stopped submitting new buffers:
+ * in this case, the refcount after decrement will eventually reach 1
+ * so here it is 2.
+ * We also trigger polling periodically after each 16 packets
+ * (the value 16 here is more or less arbitrary, it's tuned to trigger
+ * less than 10% of times).
+ */
+ if (cnt <= 2 || !(cnt % 16))
+ vhost_poll_queue(&vq->poll);
/* set len to mark this desc buffers done DMA */
vq->heads[ubuf->desc].len = status ?
VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN;
It seems that to avoid deadlocks it is enough to poll vq before we are going to use the last buffer. This is faster than c70aa540c7a9f67add11ad3161096fb95233aa2e. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- drivers/vhost/net.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)