Hi Cheng,
Some comments inline.
> -----Original Message-----
> From: Jiang, Cheng1 <cheng1.ji...@intel.com>
> Sent: Monday, April 12, 2021 7:34 PM
> To: maxime.coque...@redhat.com; Xia, Chenbo <chenbo....@intel.com>
> Cc: dev@dpdk.org; Hu, Jiayu <jiayu...@intel.com>; Yang, YvonneX
> <yvonnex.y...@intel.com>; Wang, Yinan <yinan.w...@intel.com>; Liu,
> Yong <yong....@intel.com>; Jiang, Cheng1 <cheng1.ji...@intel.com>
> Subject: [PATCH v5 1/4] vhost: abstract and reorganize async split ring code
>
> In order to improve code efficiency and readability when async packed
> ring support is enabled. This patch abstract some functions like
> shadow_ring_store and write_back_completed_descs_split. And improve
> the efficiency of some pointer offset calculation.
Need to improve grammar for commit log, as there is typo and incomplete
sentence.
>
> Signed-off-by: Cheng Jiang <cheng1.ji...@intel.com>
> ---
> lib/librte_vhost/virtio_net.c | 146 +++++++++++++++++++---------------
> 1 file changed, 84 insertions(+), 62 deletions(-)
>
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index ff3987860..c43ab0093 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -1458,6 +1458,29 @@ virtio_dev_rx_async_get_info_idx(uint16_t
> pkts_idx,
> (vq_size - n_inflight + pkts_idx) & (vq_size - 1);
> }
>
> +static __rte_always_inline void
> +shadow_ring_store(struct vhost_virtqueue *vq, void *shadow_ring, void
> *d_ring,
> + uint16_t s_idx, uint16_t d_idx,
> + uint16_t count, uint16_t elem_size)
> +{
> + if (d_idx + count <= vq->size) {
> + rte_memcpy((void *)((uintptr_t)d_ring + d_idx * elem_size),
> + (void *)((uintptr_t)shadow_ring + s_idx * elem_size),
> + count * elem_size);
> + } else {
> + uint16_t size = vq->size - d_idx;
> +
> + rte_memcpy((void *)((uintptr_t)d_ring + d_idx * elem_size),
> + (void *)((uintptr_t)shadow_ring + s_idx * elem_size),
> + size * elem_size);
> +
> + rte_memcpy((void *)((uintptr_t)d_ring),
> + (void *)((uintptr_t)shadow_ring +
> + (s_idx + size) * elem_size),
> + (count - size) * elem_size);
> + }
> +}
> +
> static __rte_noinline uint32_t
> virtio_dev_rx_async_submit_split(struct virtio_net *dev,
> struct vhost_virtqueue *vq, uint16_t queue_id,
> @@ -1478,6 +1501,7 @@ virtio_dev_rx_async_submit_split(struct virtio_net
> *dev,
> struct rte_vhost_iov_iter *dst_it = it_pool + 1;
> uint16_t slot_idx = 0;
> uint16_t segs_await = 0;
> + uint16_t iovec_idx = 0, it_idx = 0;
> struct async_inflight_info *pkts_info = vq->async_pkts_info;
> uint32_t n_pkts = 0, pkt_err = 0;
> uint32_t num_async_pkts = 0, num_done_pkts = 0;
> @@ -1513,27 +1537,32 @@ virtio_dev_rx_async_submit_split(struct
> virtio_net *dev,
>
> if (async_mbuf_to_desc(dev, vq, pkts[pkt_idx],
> buf_vec, nr_vec, num_buffers,
> - src_iovec, dst_iovec, src_it, dst_it) < 0) {
> + &src_iovec[iovec_idx],
> + &dst_iovec[iovec_idx],
> + &src_it[it_idx],
> + &dst_it[it_idx]) < 0) {
When use index, it's strange to get src and dst iov_iter from dst_it and src_it
respectively,
as they are not start addresses of two separated iov_iter arrays but have
overlapped
elements. IMO, there is no need to use src/dst_it, as they can be simply
indexed by
it_pool[it_idx] and it_pool[it_idx+1].
> vq->shadow_used_idx -= num_buffers;
> break;
> }
>
> slot_idx = (vq->async_pkts_idx + num_async_pkts) &
> (vq->size - 1);
> - if (src_it->count) {
> + if (src_it[it_idx].count) {
> uint16_t from, to;
>
> - async_fill_desc(&tdes[pkt_burst_idx++], src_it, dst_it);
> + async_fill_desc(&tdes[pkt_burst_idx++],
> + &src_it[it_idx],
> + &dst_it[it_idx]);
> pkts_info[slot_idx].descs = num_buffers;
> pkts_info[slot_idx].mbuf = pkts[pkt_idx];
> async_pkts_log[num_async_pkts].pkt_idx = pkt_idx;
> async_pkts_log[num_async_pkts++].last_avail_idx =
> vq->last_avail_idx;
> - src_iovec += src_it->nr_segs;
> - dst_iovec += dst_it->nr_segs;
> - src_it += 2;
> - dst_it += 2;
> - segs_await += src_it->nr_segs;
> +
> + iovec_idx += src_it[it_idx].nr_segs;
> + it_idx += 2;
> +
> + segs_await += src_it[it_idx].nr_segs;
>
> /**
> * recover shadow used ring and keep DMA-occupied
> @@ -1541,23 +1570,12 @@ virtio_dev_rx_async_submit_split(struct
> virtio_net *dev,
> */
> from = vq->shadow_used_idx - num_buffers;
> to = vq->async_desc_idx & (vq->size - 1);
> - if (num_buffers + to <= vq->size) {
> - rte_memcpy(&vq->async_descs_split[to],
> - &vq-
> >shadow_used_split[from],
> - num_buffers *
> - sizeof(struct
> vring_used_elem));
> - } else {
> - int size = vq->size - to;
> -
> - rte_memcpy(&vq->async_descs_split[to],
> - &vq-
> >shadow_used_split[from],
> - size *
> - sizeof(struct
> vring_used_elem));
> - rte_memcpy(vq->async_descs_split,
> - &vq-
> >shadow_used_split[from +
> - size], (num_buffers - size) *
> - sizeof(struct vring_used_elem));
> - }
> +
> + shadow_ring_store(vq, vq->shadow_used_split,
> + vq->async_descs_split,
> + from, to, num_buffers,
> + sizeof(struct vring_used_elem));
This function is to store DMA-occupied desc, but " shadow_ring_store" is not a
good name
for it. In addition, I think there is no need to pass vq as a parameter. What
you need is the
size of shadow ring and async desc ring.
Thanks,
Jiayu
> +
> vq->async_desc_idx += num_buffers;
> vq->shadow_used_idx -= num_buffers;
> } else
> @@ -1575,10 +1593,9 @@ virtio_dev_rx_async_submit_split(struct
> virtio_net *dev,
> BUF_VECTOR_MAX))) {
> n_pkts = vq->async_ops.transfer_data(dev->vid,
> queue_id, tdes, 0, pkt_burst_idx);
> - src_iovec = vec_pool;
> - dst_iovec = vec_pool + (VHOST_MAX_ASYNC_VEC >>
> 1);
> - src_it = it_pool;
> - dst_it = it_pool + 1;
> + iovec_idx = 0;
> + it_idx = 0;
> +
> segs_await = 0;
> vq->async_pkts_inflight_n += n_pkts;
>
> @@ -1639,6 +1656,43 @@ virtio_dev_rx_async_submit_split(struct
> virtio_net *dev,
> return pkt_idx;
> }
>
> +static __rte_always_inline void
> +write_back_completed_descs_split(struct vhost_virtqueue *vq, uint16_t
> n_descs)
> +{
> + uint16_t nr_left = n_descs;
> + uint16_t nr_copy;
> + uint16_t to, from;
> +
> + do {
> + from = vq->last_async_desc_idx & (vq->size - 1);
> + nr_copy = nr_left + from <= vq->size ? nr_left :
> + vq->size - from;
> + to = vq->last_used_idx & (vq->size - 1);
> +
> + if (to + nr_copy <= vq->size) {
> + rte_memcpy(&vq->used->ring[to],
> + &vq->async_descs_split[from],
> + nr_copy *
> + sizeof(struct vring_used_elem));
> + } else {
> + uint16_t size = vq->size - to;
> +
> + rte_memcpy(&vq->used->ring[to],
> + &vq->async_descs_split[from],
> + size *
> + sizeof(struct vring_used_elem));
> + rte_memcpy(vq->used->ring,
> + &vq->async_descs_split[from +
> + size], (nr_copy - size) *
> + sizeof(struct vring_used_elem));
> + }
> +
> + vq->last_async_desc_idx += nr_copy;
> + vq->last_used_idx += nr_copy;
> + nr_left -= nr_copy;
> + } while (nr_left > 0);
> +}
> +
> uint16_t rte_vhost_poll_enqueue_completed(int vid, uint16_t queue_id,
> struct rte_mbuf **pkts, uint16_t count)
> {
> @@ -1695,39 +1749,7 @@ uint16_t rte_vhost_poll_enqueue_completed(int
> vid, uint16_t queue_id,
> vq->async_pkts_inflight_n -= n_pkts_put;
>
> if (likely(vq->enabled && vq->access_ok)) {
> - uint16_t nr_left = n_descs;
> - uint16_t nr_copy;
> - uint16_t to;
> -
> - /* write back completed descriptors to used ring */
> - do {
> - from = vq->last_async_desc_idx & (vq->size - 1);
> - nr_copy = nr_left + from <= vq->size ? nr_left :
> - vq->size - from;
> - to = vq->last_used_idx & (vq->size - 1);
> -
> - if (to + nr_copy <= vq->size) {
> - rte_memcpy(&vq->used->ring[to],
> - &vq-
> >async_descs_split[from],
> - nr_copy *
> - sizeof(struct
> vring_used_elem));
> - } else {
> - uint16_t size = vq->size - to;
> -
> - rte_memcpy(&vq->used->ring[to],
> - &vq-
> >async_descs_split[from],
> - size *
> - sizeof(struct
> vring_used_elem));
> - rte_memcpy(vq->used->ring,
> - &vq->async_descs_split[from
> +
> - size], (nr_copy - size) *
> - sizeof(struct
> vring_used_elem));
> - }
> -
> - vq->last_async_desc_idx += nr_copy;
> - vq->last_used_idx += nr_copy;
> - nr_left -= nr_copy;
> - } while (nr_left > 0);
> + write_back_completed_descs_split(vq, n_descs);
>
> __atomic_add_fetch(&vq->used->idx, n_descs,
> __ATOMIC_RELEASE);
> vhost_vring_call_split(dev, vq);
> --
> 2.29.2
