On 05.09.2019 19:14, Marvin Liu wrote:
> Burst enqueue function will first check whether descriptors are cache
> aligned. It will also check prerequisites in the beginning. Burst
> enqueue function not support chained mbufs, single packet enqueue
> function will handle it.
>
> Signed-off-by: Marvin Liu <yong....@intel.com>
Hi.
Can we rely on loop unrolling by compiler instead of repeating each
command 4 times?
For example:
uint64_t len[PACKED_DESCS_BURST];
for (i = 0; i < PACKED_DESCS_BURST; i++)
len[i] = descs[avail_idx + i].len;
For 'if's:
res = false;
for (i = 0; i < PACKED_DESCS_BURST; i++)
res |= pkts[i]->next != NULL;
if (unlikely(res))
return -1;
or just
for (i = 0; i < PACKED_DESCS_BURST; i++)
if (unlikely(pkts[i]->next != NULL))
return -1;
Since PACKED_DESCS_BURST is a fairly small constant, loops should be
unrolled by compiler producing almost same code.
This will significantly reduce code size and will also allow to
play with PACKED_DESCS_BURST value without massive code changes.
Same is applicable to other patches in the series.
What do you think?
Best regards, Ilya Maximets.
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 884befa85..ed8b4aabf 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -39,6 +39,8 @@
>
> #define VHOST_LOG_CACHE_NR 32
>
> +#define PACKED_DESCS_BURST 4
> +#define PACKED_BURST_MASK (PACKED_DESCS_BURST - 1)
> /**
> * Structure contains buffer address, length and descriptor index
> * from vring to do scatter RX.
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 5ad0a8175..51ed20543 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -896,6 +896,106 @@ virtio_dev_rx_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
> return pkt_idx;
> }
>
> +static __rte_unused uint16_t
> +virtio_dev_rx_burst_packed(struct virtio_net *dev, struct vhost_virtqueue
> *vq,
> + struct rte_mbuf **pkts)
> +{
> + bool wrap_counter = vq->avail_wrap_counter;
> + struct vring_packed_desc *descs = vq->desc_packed;
> + uint16_t avail_idx = vq->last_avail_idx;
> + uint64_t desc_addr, desc_addr1, desc_addr2, desc_addr3;
> + uint64_t len, len1, len2, len3;
> + struct virtio_net_hdr_mrg_rxbuf *hdr, *hdr1, *hdr2, *hdr3;
> + uint32_t buf_offset = dev->vhost_hlen;
> +
> + if (unlikely(avail_idx & PACKED_BURST_MASK))
> + return -1;
> +
> + if (unlikely((pkts[0]->next != NULL) |
> + (pkts[1]->next != NULL) |
> + (pkts[2]->next != NULL) |
> + (pkts[3]->next != NULL)))
> + return -1;
> +
> + if (unlikely(!desc_is_avail(&descs[avail_idx], wrap_counter)) |
> + unlikely(!desc_is_avail(&descs[avail_idx + 1], wrap_counter)) |
> + unlikely(!desc_is_avail(&descs[avail_idx + 2], wrap_counter)) |
> + unlikely(!desc_is_avail(&descs[avail_idx + 3], wrap_counter)))
> + return 1;
> +
> + rte_smp_rmb();
> +
> + len = descs[avail_idx].len;
> + len1 = descs[avail_idx + 1].len;
> + len2 = descs[avail_idx + 2].len;
> + len3 = descs[avail_idx + 3].len;
> +
> + if (unlikely((pkts[0]->pkt_len > (len - buf_offset)) |
> + (pkts[1]->pkt_len > (len1 - buf_offset)) |
> + (pkts[2]->pkt_len > (len2 - buf_offset)) |
> + (pkts[3]->pkt_len > (len3 - buf_offset))))
> + return -1;
> +
> + desc_addr = vhost_iova_to_vva(dev, vq, descs[avail_idx].addr, &len,
> + VHOST_ACCESS_RW);
> +
> + desc_addr1 = vhost_iova_to_vva(dev, vq, descs[avail_idx + 1].addr,
> + &len1, VHOST_ACCESS_RW);
> +
> + desc_addr2 = vhost_iova_to_vva(dev, vq, descs[avail_idx + 2].addr,
> + &len2, VHOST_ACCESS_RW);
> +
> + desc_addr3 = vhost_iova_to_vva(dev, vq, descs[avail_idx + 3].addr,
> + &len3, VHOST_ACCESS_RW);
> +
> + if (unlikely((len != descs[avail_idx].len) |
> + (len1 != descs[avail_idx + 1].len) |
> + (len2 != descs[avail_idx + 2].len) |
> + (len3 != descs[avail_idx + 3].len)))
> + return -1;
> +
> + rte_prefetch0((void *)(uintptr_t)desc_addr);
> + rte_prefetch0((void *)(uintptr_t)desc_addr1);
> + rte_prefetch0((void *)(uintptr_t)desc_addr2);
> + rte_prefetch0((void *)(uintptr_t)desc_addr3);
> +
> + hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr;
> + hdr1 = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr1;
> + hdr2 = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr2;
> + hdr3 = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr3;
> +
> + virtio_enqueue_offload(pkts[0], &hdr->hdr);
> + virtio_enqueue_offload(pkts[1], &hdr1->hdr);
> + virtio_enqueue_offload(pkts[2], &hdr2->hdr);
> + virtio_enqueue_offload(pkts[3], &hdr3->hdr);
> +
> + len = pkts[0]->pkt_len + dev->vhost_hlen;
> + len1 = pkts[1]->pkt_len + dev->vhost_hlen;
> + len2 = pkts[2]->pkt_len + dev->vhost_hlen;
> + len3 = pkts[3]->pkt_len + dev->vhost_hlen;
> +
> + vq->last_avail_idx += PACKED_DESCS_BURST;
> + if (vq->last_avail_idx >= vq->size) {
> + vq->last_avail_idx -= vq->size;
> + vq->avail_wrap_counter ^= 1;
> + }
> +
> + rte_memcpy((void *)(uintptr_t)(desc_addr + buf_offset),
> + rte_pktmbuf_mtod_offset(pkts[0], void *, 0),
> + pkts[0]->pkt_len);
> + rte_memcpy((void *)(uintptr_t)(desc_addr1 + buf_offset),
> + rte_pktmbuf_mtod_offset(pkts[1], void *, 0),
> + pkts[1]->pkt_len);
> + rte_memcpy((void *)(uintptr_t)(desc_addr2 + buf_offset),
> + rte_pktmbuf_mtod_offset(pkts[2], void *, 0),
> + pkts[2]->pkt_len);
> + rte_memcpy((void *)(uintptr_t)(desc_addr3 + buf_offset),
> + rte_pktmbuf_mtod_offset(pkts[3], void *, 0),
> + pkts[3]->pkt_len);
> +
> + return 0;
> +}
> +
> static __rte_unused int16_t
> virtio_dev_rx_single_packed(struct virtio_net *dev, struct vhost_virtqueue
> *vq,
> struct rte_mbuf *pkt)
>
