search for: used_update

...ers/vhost/vhost.c > @@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > } > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > + struct vring_used_elem *heads, > + u16 num, bool used_update) why do you need to combine used update with prefetch? > +{ > + int ret, ret2; > + u16 last_avail_idx, last_used_idx, total, copied; > + __virtio16 avail_idx; > + struct vring_used_elem __user *used; > + int i; > + > + if (unlikely(vhost_get_avail(vq, avail_idx, &vq-&g...

...ers/vhost/vhost.c > @@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > } > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > + struct vring_used_elem *heads, > + u16 num, bool used_update) why do you need to combine used update with prefetch? > +{ > + int ret, ret2; > + u16 last_avail_idx, last_used_idx, total, copied; > + __virtio16 avail_idx; > + struct vring_used_elem __user *used; > + int i; > + > + if (unlikely(vhost_get_avail(vq, avail_idx, &vq-&g...

...vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > } > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > + struct vring_used_elem *heads, > + u16 num, bool used_update) > +{ > + int ret, ret2; > + u16 last_avail_idx, last_used_idx, total, copied; > + __virtio16 avail_idx; > + struct vring_used_elem __user *used; > + int i; > + > + if (unlikely(vhost_get_avail(vq, avail_idx, &vq->avail->idx))) {...

...vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > } > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > + struct vring_used_elem *heads, > + u16 num, bool used_update) > +{ > + int ret, ret2; > + u16 last_avail_idx, last_used_idx, total, copied; > + __virtio16 avail_idx; > + struct vring_used_elem __user *used; > + int i; > + > + if (unlikely(vhost_get_avail(vq, avail_idx, &vq->avail->idx))) {...

...struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > > > } > > > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > > > + struct vring_used_elem *heads, > > > + u16 num, bool used_update) > > why do you need to combine used update with prefetch? > > For better performance Why is sticking a branch in there better than requesting the update conditionally from the caller? > and I believe we don't care about the overhead when > we meet errors in tx. That...

...struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > > > } > > > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > > > + struct vring_used_elem *heads, > > > + u16 num, bool used_update) > > why do you need to combine used update with prefetch? > > For better performance Why is sticking a branch in there better than requesting the update conditionally from the caller? > and I believe we don't care about the overhead when > we meet errors in tx. That...

...a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, } EXPORT_SYMBOL_GPL(vhost_dequeue_msg); +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, + struct vring_used_elem *heads, + u16 num, bool used_update) +{ + int ret, ret2; + u16 last_avail_idx, last_used_idx, total, copied; + __virtio16 avail_idx; + struct vring_used_elem __user *used; + int i; + + if (unlikely(vhost_get_avail(vq, avail_idx, &vq->avail->idx))) { + vq_err(vq, "Failed to access avail idx at %p\n", + &am...

...2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, >> } >> EXPORT_SYMBOL_GPL(vhost_dequeue_msg); >> >> +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, >> + struct vring_used_elem *heads, >> + u16 num, bool used_update) > why do you need to combine used update with prefetch? For better performance and I believe we don't care about the overhead when we meet errors in tx. > >> +{ >> + int ret, ret2; >> + u16 last_avail_idx, last_used_idx, total, copied; >> + __virtio16 avail_idx...

...ers/vhost/vhost.c > @@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > } > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > + struct vring_used_elem *heads, > + u16 num, bool used_update) Missing doc comment. > +{ > + int ret, ret2; > + u16 last_avail_idx, last_used_idx, total, copied; > + __virtio16 avail_idx; > + struct vring_used_elem __user *used; > + int i; The following variable names are a little confusing: last_avail_idx vs vq->last_avail_idx. last...

...ers/vhost/vhost.c > @@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev, > } > EXPORT_SYMBOL_GPL(vhost_dequeue_msg); > > +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq, > + struct vring_used_elem *heads, > + u16 num, bool used_update) Missing doc comment. > +{ > + int ret, ret2; > + u16 last_avail_idx, last_used_idx, total, copied; > + __virtio16 avail_idx; > + struct vring_used_elem __user *used; > + int i; The following variable names are a little confusing: last_avail_idx vs vq->last_avail_idx. last...

Hi: This series tries to implement basic tx batched processing. This is done by prefetching descriptor indices and update used ring in a batch. This intends to speed up used ring updating and improve the cache utilization. Test shows about ~22% improvement in tx pss. Please review. Jason Wang (5): vhost: split out ring head fetching logic vhost: introduce helper to prefetch desc index

Hi: This series tries to implement basic tx batched processing. This is done by prefetching descriptor indices and update used ring in a batch. This intends to speed up used ring updating and improve the cache utilization. Test shows about ~22% improvement in tx pss. Please review. Jason Wang (5): vhost: split out ring head fetching logic vhost: introduce helper to prefetch desc index