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 <qtxuning1999@sjtu.edu.cn>
---
 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);
 }
-- 
2.17.1

在 2022/8/17 21:57, Guo Zhi 写道:
> 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 <qtxuning1999@sjtu.edu.cn>
> ---
>   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);


Though it's a test device, it would be better to try avoid memory 
allocation in the datapath.

And where is is freed?

Thanks


> +	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);
>   }

On Wed, Aug 17, 2022 at 3:58 PM Guo Zhi <qtxuning1999@sjtu.edu.cn> wrote:
>
> 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 <qtxuning1999@sjtu.edu.cn>
> ---
>  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);

It seems to me we can use kmalloc_array here.

Thanks!

> +       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);
>  }
> --
> 2.17.1
>