[RFC 3/5] vhost_test: batch used buffer

[Guo Zhi <qtxuning1999@sjtu.edu.cn>]

Only add to used ring when a batch a buffer have all been used.  And if
in order feature negotiated, add randomness to the used buffer's order,
test the ability of vhost to reorder batched buffer.

Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
---
 drivers/vhost/test.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index bc8e7fb1e..1c9c40c11 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 +87,21 @@ 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) {
+		if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && batch_idx >= 2) {
+			vhost_add_used_and_signal_n(&n->dev, vq, &heads[batch_idx / 2],
+						    batch_idx - batch_idx / 2);
+			vhost_add_used_and_signal_n(&n->dev, vq, heads, batch_idx / 2);
+		} else {
+			vhost_add_used_and_signal_n(&n->dev, vq, heads, batch_idx);
+		}
+	}
 
 	mutex_unlock(&vq->mutex);
 }
-- 
2.17.1