vhost: introduce vhost_exceeds_weight()

We used to have vhost_exceeds_weight() for vhost-net to:

- prevent vhost kthread from hogging the cpu
- balance the time spent between TX and RX

This function could be useful for vsock and scsi as well. So move it
to vhost.c. Device must specify a weight which counts the number of
requests, or it can also specific a byte_weight which counts the
number of bytes that has been processed.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1e3ed41ae1f3..3f3eac4bcc58 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -413,8 +413,24 @@ static void vhost_dev_free_iovecs(struct vhost_dev *dev)
                 vhost_vq_free_iovecs(dev->vqs[i]);
 }
 
+bool vhost_exceeds_weight(struct vhost_virtqueue *vq,
+                          int pkts, int total_len)
+{
+        struct vhost_dev *dev = vq->dev;
+
+        if ((dev->byte_weight && total_len >= dev->byte_weight) ||
+            pkts >= dev->weight) {
+                vhost_poll_queue(&vq->poll);
+                return true;
+        }
+
+        return false;
+}
+EXPORT_SYMBOL_GPL(vhost_exceeds_weight);
+
 void vhost_dev_init(struct vhost_dev *dev,
-                    struct vhost_virtqueue **vqs, int nvqs, int iov_limit)
+                    struct vhost_virtqueue **vqs, int nvqs,
+                    int iov_limit, int weight, int byte_weight)
 {
         struct vhost_virtqueue *vq;
         int i;
@@ -428,6 +444,8 @@ void vhost_dev_init(struct vhost_dev *dev,
         dev->mm = NULL;
         dev->worker = NULL;
         dev->iov_limit = iov_limit;
+        dev->weight = weight;
+        dev->byte_weight = byte_weight;
         init_llist_head(&dev->work_list);
         init_waitqueue_head(&dev->wait);
         INIT_LIST_HEAD(&dev->read_list);