Re: [RFC v2 2/7] vhost_test: batch used buffer

Only add to used ring when a batch of buffer have all been used.  And if
in order feature negotiated, only add the last used descriptor for a
batch of buffer.

Signed-off-by: Guo Zhi <redacted>
---
  drivers/vhost/test.c | 8 +++++++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index bc8e7fb1e635..57cdb3a3edf6 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c

@@ -43,6 +43,9 @@ struct vhost_test {
  static void handle_vq(struct vhost_test *n)
  {
  	struct vhost_virtqueue *vq = &n->vqs[VHOST_TEST_VQ];
+	struct vring_used_elem *heads = kmalloc(sizeof(*heads)
+			* vq->num, GFP_KERNEL);

+	int batch_idx = 0;
  	unsigned out, in;
  	int head;
  	size_t len, total_len = 0;

@@ -84,11 +87,14 @@ static void handle_vq(struct vhost_test *n)
  			vq_err(vq, "Unexpected 0 len for TX\n");
  			break;
  		}
-		vhost_add_used_and_signal(&n->dev, vq, head, 0);
+		heads[batch_idx].id = cpu_to_vhost32(vq, head);
+		heads[batch_idx++].len = cpu_to_vhost32(vq, len);
  		total_len += len;
  		if (unlikely(vhost_exceeds_weight(vq, 0, total_len)))
  			break;
  	}
+	if (batch_idx)
+		vhost_add_used_and_signal_n(&n->dev, vq, heads, batch_idx);
  
  	mutex_unlock(&vq->mutex);
  }