On Mon, Aug 29, 2016 at 11:36:00PM -0400, Zhihong Wang wrote:
> This patch implements the vhost logic from scratch into a single function
> designed for high performance and better maintainability.
>
> This is the baseline version of the new code, more optimization will be
> added in the following patches in this patch set.
>
> ---
> Changes in v4:
>
> 1. Refactor the code for clearer logic.
>
> 2. Add PRINT_PACKET for debugging.
>
> ---
> Changes in v3:
>
> 1. Rewrite enqueue and delete the obsolete in the same patch.
Change log should go ---->
> Signed-off-by: Zhihong Wang <zhihong.wang at intel.com>
> ---
... here, after the SoB.
> lib/librte_vhost/vhost_rxtx.c | 525
> ++++++++++++------------------------------
> 1 file changed, 145 insertions(+), 380 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
> index 5806f99..629e8ae 100644
> --- a/lib/librte_vhost/vhost_rxtx.c
> +++ b/lib/librte_vhost/vhost_rxtx.c
> @@ -91,7 +91,7 @@ is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t
> qp_nb)
> return (is_tx ^ (idx & 1)) == 0 && idx < qp_nb * VIRTIO_QNUM;
> }
>
> -static void
> +static inline void __attribute__((always_inline))
> virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr
> *net_hdr)
> {
> if (m_buf->ol_flags & PKT_TX_L4_MASK) {
> @@ -112,6 +112,10 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct
> virtio_net_hdr *net_hdr)
> cksum));
> break;
> }
> + } else {
> + net_hdr->flags = 0;
> + net_hdr->csum_start = 0;
> + net_hdr->csum_offset = 0;
> }
>
> if (m_buf->ol_flags & PKT_TX_TCP_SEG) {
> @@ -122,437 +126,198 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct
> virtio_net_hdr *net_hdr)
> net_hdr->gso_size = m_buf->tso_segsz;
> net_hdr->hdr_len = m_buf->l2_len + m_buf->l3_len
> + m_buf->l4_len;
> + } else {
> + net_hdr->gso_type = 0;
> + net_hdr->hdr_len = 0;
> + net_hdr->gso_size = 0;
> }
> }
>
> -static inline void
> -copy_virtio_net_hdr(struct virtio_net *dev, uint64_t desc_addr,
> - struct virtio_net_hdr_mrg_rxbuf hdr)
> +static inline void __attribute__((always_inline))
> +update_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq,
> + uint32_t desc_chain_head, uint32_t desc_chain_len)
> {
> - if (dev->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf))
> - *(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr = hdr;
> - else
> - *(struct virtio_net_hdr *)(uintptr_t)desc_addr = hdr.hdr;
> + uint32_t used_idx_round = vq->last_used_idx & (vq->size - 1);
I'd suggest to use "used_idx", instead of "used_idx_round".
> +
> + vq->used->ring[used_idx_round].id = desc_chain_head;
> + vq->used->ring[used_idx_round].len = desc_chain_len;
> + vhost_log_used_vring(dev, vq, offsetof(struct vring_used,
> + ring[used_idx_round]),
> + sizeof(vq->used->ring[used_idx_round]));
> }
>
> -static inline int __attribute__((always_inline))
> -copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
> - struct rte_mbuf *m, uint16_t desc_idx)
> +static inline uint32_t __attribute__((always_inline))
> +enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq,
> + uint16_t avail_idx, struct rte_mbuf *mbuf,
> + uint32_t is_mrg_rxbuf)
> {
> - uint32_t desc_avail, desc_offset;
> - uint32_t mbuf_avail, mbuf_offset;
> - uint32_t cpy_len;
> + struct virtio_net_hdr_mrg_rxbuf *virtio_hdr;
> struct vring_desc *desc;
> uint64_t desc_addr;
> - struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
> -
> - desc = &vq->desc[desc_idx];
> + uint32_t desc_chain_head;
> + uint32_t desc_chain_len;
> + uint32_t desc_current;
> + uint32_t desc_offset;
> + uint32_t mbuf_len;
> + uint32_t mbuf_avail;
> + uint32_t copy_len;
> + uint32_t extra_buffers = 0;
I'd name it to "num_buffers", to keep consistent with the virito hdr
naming style.
> +
> + /* start with the first mbuf of the packet */
> + mbuf_len = rte_pktmbuf_data_len(mbuf);
> + mbuf_avail = mbuf_len;
> +
> + /* get the current desc */
> + desc_current = vq->avail->ring[(vq->last_used_idx) & (vq->size - 1)];
> + desc_chain_head = desc_current;
> + desc = &vq->desc[desc_current];
> desc_addr = gpa_to_vva(dev, desc->addr);
> - /*
> - * Checking of 'desc_addr' placed outside of 'unlikely' macro to avoid
> - * performance issue with some versions of gcc (4.8.4 and 5.3.0) which
> - * otherwise stores offset on the stack instead of in a register.
> - */
> - if (unlikely(desc->len < dev->vhost_hlen) || !desc_addr)
> - return -1;
> + if (unlikely(!desc_addr))
> + goto error;
>
> - rte_prefetch0((void *)(uintptr_t)desc_addr);
> + /* handle virtio header */
> + virtio_hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr;
> + virtio_enqueue_offload(mbuf, &(virtio_hdr->hdr));
> + if (is_mrg_rxbuf)
> + virtio_hdr->num_buffers = extra_buffers + 1;
>
> - virtio_enqueue_offload(m, &virtio_hdr.hdr);
> - copy_virtio_net_hdr(dev, desc_addr, virtio_hdr);
> vhost_log_write(dev, desc->addr, dev->vhost_hlen);
> PRINT_PACKET(dev, (uintptr_t)desc_addr, dev->vhost_hlen, 0);
> -
> desc_offset = dev->vhost_hlen;
> - desc_avail = desc->len - dev->vhost_hlen;
> -
> - mbuf_avail = rte_pktmbuf_data_len(m);
> - mbuf_offset = 0;
> - while (mbuf_avail != 0 || m->next != NULL) {
> - /* done with current mbuf, fetch next */
> - if (mbuf_avail == 0) {
> - m = m->next;
> -
> - mbuf_offset = 0;
> - mbuf_avail = rte_pktmbuf_data_len(m);
> + desc_chain_len = desc_offset;
> + desc_addr += desc_offset;
> +
> + /* start copy from mbuf to desc */
> + while (mbuf_avail || mbuf->next) {
> + /* get the next mbuf if the current done */
> + if (!mbuf_avail) {
> + mbuf = mbuf->next;
> + mbuf_len = rte_pktmbuf_data_len(mbuf);
> + mbuf_avail = mbuf_len;
> }
>
> - /* done with current desc buf, fetch next */
> - if (desc_avail == 0) {
> - if ((desc->flags & VRING_DESC_F_NEXT) == 0) {
> - /* Room in vring buffer is not enough */
> - return -1;
> - }
> - if (unlikely(desc->next >= vq->size))
> - return -1;
> + /* get the next desc if the current done */
> + if (desc->len <= desc_offset) {
> + if (desc->flags & VRING_DESC_F_NEXT) {
> + /* go on with the current desc chain */
> + desc_offset = 0;
> + desc_current = desc->next;
> + desc = &vq->desc[desc_current];
> + desc_addr = gpa_to_vva(dev, desc->addr);
> + if (unlikely(!desc_addr))
> + goto error;
> + } else if (is_mrg_rxbuf) {
> + /* start with the next desc chain */
> + update_used_ring(dev, vq, desc_chain_head,
> + desc_chain_len);
> + vq->last_used_idx++;
Why not putting "vq->last_used_idx++" into update_used_ring()?
> + extra_buffers++;
> + virtio_hdr->num_buffers++;
> + if (avail_idx == vq->last_used_idx)
> + goto error;
> +
> + desc_current =
> + vq->avail->ring[(vq->last_used_idx) &
> + (vq->size - 1)];
> + desc_chain_head = desc_current;
> + desc = &vq->desc[desc_current];
> + desc_addr = gpa_to_vva(dev, desc->addr);
> + if (unlikely(!desc_addr))
> + goto error;
>
> - desc = &vq->desc[desc->next];
> - desc_addr = gpa_to_vva(dev, desc->addr);
> - if (unlikely(!desc_addr))
> - return -1;
> -
> - desc_offset = 0;
> - desc_avail = desc->len;
> + desc_chain_len = 0;
> + desc_offset = 0;
> + } else
> + goto error;
> }
>
> - cpy_len = RTE_MIN(desc_avail, mbuf_avail);
> - rte_memcpy((void *)((uintptr_t)(desc_addr + desc_offset)),
> - rte_pktmbuf_mtod_offset(m, void *, mbuf_offset),
> - cpy_len);
> - vhost_log_write(dev, desc->addr + desc_offset, cpy_len);
> - PRINT_PACKET(dev, (uintptr_t)(desc_addr + desc_offset),
> - cpy_len, 0);
> -
> - mbuf_avail -= cpy_len;
> - mbuf_offset += cpy_len;
> - desc_avail -= cpy_len;
> - desc_offset += cpy_len;
> + /* copy mbuf data */
> + copy_len = RTE_MIN(desc->len - desc_offset, mbuf_avail);
TBH, I'm okay with copy_len (actually, I prefer it slightly). However,
the old code uses cpy_len, the current dequeue function also uses cpy_len,
I then see no good reason to use copy_len here. It's really not a good
idea to me to use two different naming styles in one source file.
> + rte_memcpy((void *)(uintptr_t)desc_addr,
> + rte_pktmbuf_mtod_offset(mbuf, void *,
> + mbuf_len - mbuf_avail),
I would keep the old var "mbuf_offset" and do not introduce "mbuf_len".
This could avoid above calculation and make it straightforward.
> + copy_len);
> + vhost_log_write(dev, desc->addr + desc_offset, copy_len);
> + PRINT_PACKET(dev, (uintptr_t)desc_addr, copy_len, 0);
> + mbuf_avail -= copy_len;
> + desc_offset += copy_len;
> + desc_addr += copy_len;
> + desc_chain_len += copy_len;
Vertical alighment[0] is not a must, but as you can see, it's a style I
prefer. Meaning, if possible, please follow it.
[0]: https://en.wikipedia.org/wiki/Programming_style#Vertical_alignment
> }
>
> - return 0;
> -}
> + update_used_ring(dev, vq, desc_chain_head, desc_chain_len);
> + vq->last_used_idx++;
>
...
> - rte_prefetch0(&vq->desc[desc_indexes[0]]);
> - for (i = 0; i < count; i++) {
> - uint16_t desc_idx = desc_indexes[i];
> - int err;
> + return 0;
>
> - err = copy_mbuf_to_desc(dev, vq, pkts[i], desc_idx);
> - if (unlikely(err)) {
> - used_idx = (start_idx + i) & (vq->size - 1);
> - vq->used->ring[used_idx].len = dev->vhost_hlen;
> - vhost_log_used_vring(dev, vq,
> - offsetof(struct vring_used, ring[used_idx]),
> - sizeof(vq->used->ring[used_idx]));
> - }
> +error:
> + /* rollback on any error if last_used_idx update on-the-fly */
> + vq->last_used_idx -= extra_buffers;
>
> - if (i + 1 < count)
> - rte_prefetch0(&vq->desc[desc_indexes[i+1]]);
> - }
> + return 1;
We normally returns -1 (but not 1) on error.
>
> +static inline void __attribute__((always_inline))
> +notify_guest(struct virtio_net *dev, struct vhost_virtqueue *vq)
> +{
> rte_smp_wmb();
> -
> - *(volatile uint16_t *)&vq->used->idx += count;
> - vq->last_used_idx += count;
> - vhost_log_used_vring(dev, vq,
> - offsetof(struct vring_used, idx),
> - sizeof(vq->used->idx));
> -
> - /* flush used->idx update before we read avail->flags. */
> + vq->used->idx = vq->last_used_idx;
I will not drop the "volatile" cast here, sliently. You know this kind of
stuff is tricky and would be painful to debug if it cause any issue. Such
removal deserves a patch, as well as some explanations.
> + vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
> + sizeof(vq->used->idx));
> rte_mb();
> -
> - /* Kick the guest if necessary. */
> if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> && (vq->callfd >= 0))
> eventfd_write(vq->callfd, (eventfd_t)1);
> - return count;
> }
>
...
> + /* start enqueuing packets 1 by 1 */
> + avail_idx = *((volatile uint16_t *)&vq->avail->idx);
> + while (pkt_left && avail_idx != vq->last_used_idx) {
> + if (enqueue_packet(dev, vq, avail_idx, pkts[pkt_idx],
> + is_mrg_rxbuf))
> break;
> - }
> -
> - nr_used = copy_mbuf_to_desc_mergeable(dev, vq, end,
> - pkts[pkt_idx], buf_vec);
> - rte_smp_wmb();
> -
> - *(volatile uint16_t *)&vq->used->idx += nr_used;
> - vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
> - sizeof(vq->used->idx));
> - vq->last_used_idx += nr_used;
> - }
> -
> - if (likely(pkt_idx)) {
> - /* flush used->idx update before we read avail->flags. */
> - rte_mb();
>
> - /* Kick the guest if necessary. */
> - if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> - && (vq->callfd >= 0))
> - eventfd_write(vq->callfd, (eventfd_t)1);
> + pkt_idx++;
> + pkt_sent++;
pkt_idx and pkt_sent is duplicate here.
--yliu
> + pkt_left--;
> }
>
> - return pkt_idx;
> -}
> -
> -uint16_t
> -rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
> - struct rte_mbuf **pkts, uint16_t count)
> -{
> - struct virtio_net *dev = get_device(vid);
> -
> - if (!dev)
> - return 0;
> + /* update used idx and kick the guest if necessary */
> + if (pkt_sent)
> + notify_guest(dev, vq);
>
> - if (dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF))
> - return virtio_dev_merge_rx(dev, queue_id, pkts, count);
> - else
> - return virtio_dev_rx(dev, queue_id, pkts, count);
> + return pkt_sent;
> }
>
> static void
> --
> 2.7.4
