search for: desc_id

...s? > > > Implementation Reference: > > struct desc_iterator { > unsigned int head; > unsigned int tail; > }; > > add_first(*vq, *desc_iterator, *num_free, ..) > { > if (vq->vq.num_free < 1) > return -ENOSPC; > get_desc(&desc_id); > desc[desc_id].flag &= ~_F_NEXT; > desc_iterator->head = desc_id > desc_iterator->tail = desc_iterator->head; > *num_free = vq->vq.num_free; > } > > add_next(vq, desc_iterator, *num_free,..) > { > get_desc(&desc_id); > de...

...s? > > > Implementation Reference: > > struct desc_iterator { > unsigned int head; > unsigned int tail; > }; > > add_first(*vq, *desc_iterator, *num_free, ..) > { > if (vq->vq.num_free < 1) > return -ENOSPC; > get_desc(&desc_id); > desc[desc_id].flag &= ~_F_NEXT; > desc_iterator->head = desc_id > desc_iterator->tail = desc_iterator->head; > *num_free = vq->vq.num_free; > } > > add_next(vq, desc_iterator, *num_free,..) > { > get_desc(&desc_id); > de...

...)) { > > add_last(vq, ...) > > kick > > wait > > } > > "!add_next(vq, ...)" means that the vq is full? No - it means there's only 1 entry left for the last descriptor. > If so, what would add_last() > do then? > > > Using VIRTQUEUE_DESC_ID_INIT seems to avoid a branch in the driver, but > > in fact it merely puts the branch in the virtio code. > > > > Actually it wasn't intended to improve performance. It is used to indicate > the "init" state > of the chain. So, when virtqueue_add_chain_desc(,...

...)) { > > add_last(vq, ...) > > kick > > wait > > } > > "!add_next(vq, ...)" means that the vq is full? No - it means there's only 1 entry left for the last descriptor. > If so, what would add_last() > do then? > > > Using VIRTQUEUE_DESC_ID_INIT seems to avoid a branch in the driver, but > > in fact it merely puts the branch in the virtio code. > > > > Actually it wasn't intended to improve performance. It is used to indicate > the "init" state > of the chain. So, when virtqueue_add_chain_desc(,...

...-- or, do you have a different thought about using the three APIs? Implementation Reference: struct desc_iterator { unsigned int head; unsigned int tail; }; add_first(*vq, *desc_iterator, *num_free, ..) { if (vq->vq.num_free < 1) return -ENOSPC; get_desc(&desc_id); desc[desc_id].flag &= ~_F_NEXT; desc_iterator->head = desc_id desc_iterator->tail = desc_iterator->head; *num_free = vq->vq.num_free; } add_next(vq, desc_iterator, *num_free,..) { get_desc(&desc_id); desc[desc_id].flag &= ~_F_NEXT; desc[...

...unsigned int head; > > > unsigned int tail; > > > }; > > > > > > add_first(*vq, *desc_iterator, *num_free, ..) > > > { > > > if (vq->vq.num_free < 1) > > > return -ENOSPC; > > > get_desc(&desc_id); > > > desc[desc_id].flag &= ~_F_NEXT; > > > desc_iterator->head = desc_id > > > desc_iterator->tail = desc_iterator->head; > > > *num_free = vq->vq.num_free; > > > } > > > > > > add_next(vq, desc_i...

...unsigned int head; > > > unsigned int tail; > > > }; > > > > > > add_first(*vq, *desc_iterator, *num_free, ..) > > > { > > > if (vq->vq.num_free < 1) > > > return -ENOSPC; > > > get_desc(&desc_id); > > > desc[desc_id].flag &= ~_F_NEXT; > > > desc_iterator->head = desc_id > > > desc_iterator->tail = desc_iterator->head; > > > *num_free = vq->vq.num_free; > > > } > > > > > > add_next(vq, desc_i...

...gt;> >> struct desc_iterator { >> unsigned int head; >> unsigned int tail; >> }; >> >> add_first(*vq, *desc_iterator, *num_free, ..) >> { >> if (vq->vq.num_free < 1) >> return -ENOSPC; >> get_desc(&desc_id); >> desc[desc_id].flag &= ~_F_NEXT; >> desc_iterator->head = desc_id >> desc_iterator->tail = desc_iterator->head; >> *num_free = vq->vq.num_free; >> } >> >> add_next(vq, desc_iterator, *num_free,..) >> { >>...

...ead; >>>> unsigned int tail; >>>> }; >>>> >>>> add_first(*vq, *desc_iterator, *num_free, ..) >>>> { >>>> if (vq->vq.num_free < 1) >>>> return -ENOSPC; >>>> get_desc(&desc_id); >>>> desc[desc_id].flag &= ~_F_NEXT; >>>> desc_iterator->head = desc_id >>>> desc_iterator->tail = desc_iterator->head; >>>> *num_free = vq->vq.num_free; >>>> } >>>> >>>> ad...