[dpdk-dev] [PATCH v2 1/7] vhost: refactor rte_vhost_dequeue_burst

[Xie, Huawei]

On 3/4/2016 10:30 AM, Yuanhan Liu wrote:
> On Thu, Mar 03, 2016 at 05:40:14PM +0000, Xie, Huawei wrote:
>> On 2/18/2016 9:48 PM, Yuanhan Liu wrote:
>>> The current rte_vhost_dequeue_burst() implementation is a bit messy
>> [...]
>>> +
>>>  uint16_t
>>>  rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
>>>  	struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count)
>>>  {
>>> -	struct rte_mbuf *m, *prev;
>>>  	struct vhost_virtqueue *vq;
>>> -	struct vring_desc *desc;
>>> -	uint64_t vb_addr = 0;
>>> -	uint64_t vb_net_hdr_addr = 0;
>>> -	uint32_t head[MAX_PKT_BURST];
>>> +	uint32_t desc_indexes[MAX_PKT_BURST];
>> indices
> http://dictionary.reference.com/browse/index
>
>     index
>     noun, plural indexes, indices 

ok, i see both two are used.


>>
>>>  	uint32_t used_idx;
>>>  	uint32_t i;
>>> -	uint16_t free_entries, entry_success = 0;
>>> +	uint16_t free_entries;
>>>  	uint16_t avail_idx;
>>> -	struct virtio_net_hdr *hdr = NULL;
>>> +	struct rte_mbuf *m;
>>>  
>>>  	if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->virt_qp_nb))) {
>>>  		RTE_LOG(ERR, VHOST_DATA,
>>> @@ -730,197 +813,49 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
>>>  		return 0;
>>>  
>>> -		if (entry_success < (free_entries - 1)) {
>>> -			/* Prefetch descriptor index. */
>>> -			rte_prefetch0(&vq->desc[head[entry_success+1]]);
>>> -			rte_prefetch0(&vq->used->ring[(used_idx + 1) & (vq->size - 1)]);
>>> -		}
>> Why is this prefetch silently dropped in the patch?
> Oops, good catching. Will fix it. Thanks.
>
>
>>>  			break;
>>> +		pkts[i] = m;
>>>  
>>> -		m->nb_segs = seg_num;
>>> -		if ((hdr->flags != 0) || (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE))
>>> -			vhost_dequeue_offload(hdr, m);
>>> -
>>> -		pkts[entry_success] = m;
>>> -		vq->last_used_idx++;
>>> -		entry_success++;
>>> +		used_idx = vq->last_used_idx++ & (vq->size - 1);
>>> +		vq->used->ring[used_idx].id  = desc_indexes[i];
>>> +		vq->used->ring[used_idx].len = 0;
>> What is the correct value for ring[used_idx].len,  the packet length or 0?
> Good question. I didn't notice that before. Sounds buggy to me. However,
> that's from the old code. Will check it.

Yes, i knew it is in old code also. Thanks.

> 	--yliu
>