[dpdk-dev] [RFC 06/14] vhost: introduce specific iovec structure

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch introduces rte_vhost_iovec struct that contains
both source and destination addresses since we always have
a 1:1 mapping between source and destination. While using
the standard iovec struct might have seemed better, having
to duplicate IO vectors and its iterators is memory
inefficient and make the implementation more complex.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 examples/vhost/ioat.c       | 24 ++++++-------
 lib/vhost/rte_vhost_async.h | 19 +++++++----
 lib/vhost/vhost.h           |  6 ++--
 lib/vhost/virtio_net.c      | 68 ++++++++++++++-----------------------
 4 files changed, 52 insertions(+), 65 deletions(-)

diff --git a/examples/vhost/ioat.c b/examples/vhost/ioat.c
index 457f8171f0..dcbcf65e4e 100644
--- a/examples/vhost/ioat.c
+++ b/examples/vhost/ioat.c
@@ -129,33 +129,31 @@ ioat_transfer_data_cb(int vid, uint16_t queue_id,
 {
 	uint32_t i_desc;
 	uint16_t dev_id = dma_bind[vid].dmas[queue_id * 2 + VIRTIO_RXQ].dev_id;
-	struct rte_vhost_iov_iter *src = NULL;
-	struct rte_vhost_iov_iter *dst = NULL;
+	struct rte_vhost_iov_iter *iter = NULL;
 	unsigned long i_seg;
 	unsigned short mask = MAX_ENQUEUED_SIZE - 1;
 	unsigned short write = cb_tracker[dev_id].next_write;
 
 	if (!opaque_data) {
 		for (i_desc = 0; i_desc < count; i_desc++) {
-			src = descs[i_desc].src;
-			dst = descs[i_desc].dst;
+			iter = descs[i_desc].iter;
 			i_seg = 0;
-			if (cb_tracker[dev_id].ioat_space < src->nr_segs)
+			if (cb_tracker[dev_id].ioat_space < iter->nr_segs)
 				break;
-			while (i_seg < src->nr_segs) {
+			while (i_seg < iter->nr_segs) {
 				rte_ioat_enqueue_copy(dev_id,
-					(uintptr_t)(src->iov[i_seg].iov_base)
-						+ src->offset,
-					(uintptr_t)(dst->iov[i_seg].iov_base)
-						+ dst->offset,
-					src->iov[i_seg].iov_len,
+					(uintptr_t)(iter->iov[i_seg].src_addr)
+						+ iter->offset,
+					(uintptr_t)(iter->iov[i_seg].dst_addr)
+						+ iter->offset,
+					iter->iov[i_seg].len,
 					0,
 					0);
 				i_seg++;
 			}
 			write &= mask;
-			cb_tracker[dev_id].size_track[write] = src->nr_segs;
-			cb_tracker[dev_id].ioat_space -= src->nr_segs;
+			cb_tracker[dev_id].size_track[write] = iter->nr_segs;
+			cb_tracker[dev_id].ioat_space -= iter->nr_segs;
 			write++;
 		}
 	} else {
diff --git a/lib/vhost/rte_vhost_async.h b/lib/vhost/rte_vhost_async.h
index 789b80f5a0..d7bb77bf90 100644
--- a/lib/vhost/rte_vhost_async.h
+++ b/lib/vhost/rte_vhost_async.h
@@ -7,6 +7,15 @@
 
 #include "rte_vhost.h"
 
+/**
+ * iovec
+ */
+struct rte_vhost_iovec {
+	void *src_addr;
+	void *dst_addr;
+	size_t len;
+};
+
 /**
  * iovec iterator
  */
@@ -16,19 +25,17 @@ struct rte_vhost_iov_iter {
 	/** total bytes of data in this iterator */
 	size_t count;
 	/** pointer to the iovec array */
-	struct iovec *iov;
+	struct rte_vhost_iovec *iov;
 	/** number of iovec in this iterator */
 	unsigned long nr_segs;
 };
 
 /**
- * dma transfer descriptor pair
+ * dma transfer descriptor
  */
 struct rte_vhost_async_desc {
-	/** source memory iov_iter */
-	struct rte_vhost_iov_iter *src;
-	/** destination memory iov_iter */
-	struct rte_vhost_iov_iter *dst;
+	/* memory iov_iter */
+	struct rte_vhost_iov_iter *iter;
 };
 
 /**
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index cb4c0f022a..dae9a1ac2d 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -132,10 +132,8 @@ struct vhost_async {
 	/* operation callbacks for DMA */
 	struct rte_vhost_async_channel_ops ops;
 
-	struct rte_vhost_iov_iter src_iov_iter[VHOST_MAX_ASYNC_IT];
-	struct rte_vhost_iov_iter dst_iov_iter[VHOST_MAX_ASYNC_IT];
-	struct iovec src_iovec[VHOST_MAX_ASYNC_VEC];
-	struct iovec dst_iovec[VHOST_MAX_ASYNC_VEC];
+	struct rte_vhost_iov_iter iov_iter[VHOST_MAX_ASYNC_IT];
+	struct rte_vhost_iovec iovec[VHOST_MAX_ASYNC_VEC];
 
 	/* data transfer status */
 	struct async_inflight_info *pkts_info;
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index a939481eaf..7b1c52ea7d 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -925,15 +925,16 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 }
 
 static __rte_always_inline void
-async_fill_vec(struct iovec *v, void *base, size_t len)
+async_fill_vec(struct rte_vhost_iovec *v, void *src, void *dst, size_t len)
 {
-	v->iov_base = base;
-	v->iov_len = len;
+	v->src_addr = src;
+	v->dst_addr = dst;
+	v->len = len;
 }
 
 static __rte_always_inline void
 async_fill_iter(struct rte_vhost_iov_iter *it, size_t count,
-	struct iovec *vec, unsigned long nr_seg)
+	struct rte_vhost_iovec *vec, unsigned long nr_seg)
 {
 	it->offset = 0;
 	it->count = count;
@@ -948,20 +949,16 @@ async_fill_iter(struct rte_vhost_iov_iter *it, size_t count,
 }
 
 static __rte_always_inline void
-async_fill_desc(struct rte_vhost_async_desc *desc,
-	struct rte_vhost_iov_iter *src, struct rte_vhost_iov_iter *dst)
+async_fill_desc(struct rte_vhost_async_desc *desc, struct rte_vhost_iov_iter *iter)
 {
-	desc->src = src;
-	desc->dst = dst;
+	desc->iter = iter;
 }
 
 static __rte_always_inline int
 async_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			struct rte_mbuf *m, struct buf_vector *buf_vec,
 			uint16_t nr_vec, uint16_t num_buffers,
-			struct iovec *src_iovec, struct iovec *dst_iovec,
-			struct rte_vhost_iov_iter *src_it,
-			struct rte_vhost_iov_iter *dst_it)
+			struct rte_vhost_iovec *iovec, struct rte_vhost_iov_iter *iter)
 {
 	struct rte_mbuf *hdr_mbuf;
 	struct virtio_net_hdr_mrg_rxbuf tmp_hdr, *hdr = NULL;
@@ -1075,11 +1072,9 @@ async_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 				goto out;
 			}
 
-			async_fill_vec(src_iovec + tvec_idx,
+			async_fill_vec(iovec + tvec_idx,
 				(void *)(uintptr_t)rte_pktmbuf_iova_offset(m,
-				mbuf_offset), (size_t)mapped_len);
-			async_fill_vec(dst_iovec + tvec_idx,
-					hpa, (size_t)mapped_len);
+				mbuf_offset), hpa, (size_t)mapped_len);
 
 			tlen += (uint32_t)mapped_len;
 			cpy_len -= (uint32_t)mapped_len;
@@ -1091,8 +1086,7 @@ async_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		}
 	}
 
-	async_fill_iter(src_it, tlen, src_iovec, tvec_idx);
-	async_fill_iter(dst_it, tlen, dst_iovec, tvec_idx);
+	async_fill_iter(iter, tlen, iovec, tvec_idx);
 out:
 	return error;
 }
@@ -1509,11 +1503,9 @@ virtio_dev_rx_async_submit_split(struct virtio_net *dev,
 	uint16_t avail_head;
 
 	struct vhost_async *async = vq->async;
-	struct rte_vhost_iov_iter *src_iter = async->src_iov_iter;
-	struct rte_vhost_iov_iter *dst_iter = async->dst_iov_iter;
+	struct rte_vhost_iov_iter *iter = async->iov_iter;
 	struct rte_vhost_async_desc tdes[MAX_PKT_BURST];
-	struct iovec *src_iovec = async->src_iovec;
-	struct iovec *dst_iovec = async->dst_iovec;
+	struct rte_vhost_iovec *iovec = async->iovec;
 	struct async_inflight_info *pkts_info = async->pkts_info;
 	uint32_t n_pkts = 0, pkt_err = 0;
 	int32_t n_xfer;
@@ -1545,19 +1537,18 @@ virtio_dev_rx_async_submit_split(struct virtio_net *dev,
 			vq->last_avail_idx + num_buffers);
 
 		if (async_mbuf_to_desc(dev, vq, pkts[pkt_idx], buf_vec, nr_vec, num_buffers,
-				&src_iovec[iovec_idx], &dst_iovec[iovec_idx],
-				&src_iter[it_idx], &dst_iter[it_idx]) < 0) {
+				&iovec[iovec_idx], &iter[it_idx]) < 0) {
 			vq->shadow_used_idx -= num_buffers;
 			break;
 		}
 
-		async_fill_desc(&tdes[pkt_burst_idx++], &src_iter[it_idx], &dst_iter[it_idx]);
+		async_fill_desc(&tdes[pkt_burst_idx++], &iter[it_idx]);
 
 		slot_idx = (async->pkts_idx + pkt_idx) & (vq->size - 1);
 		pkts_info[slot_idx].descs = num_buffers;
 		pkts_info[slot_idx].mbuf = pkts[pkt_idx];
 
-		iovec_idx += src_iter[it_idx].nr_segs;
+		iovec_idx += iter[it_idx].nr_segs;
 		it_idx++;
 
 		vq->last_avail_idx += num_buffers;
@@ -1707,9 +1698,8 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
 			    struct buf_vector *buf_vec,
 			    uint16_t *nr_descs,
 			    uint16_t *nr_buffers,
-			    struct iovec *src_iovec, struct iovec *dst_iovec,
-			    struct rte_vhost_iov_iter *src_it,
-			    struct rte_vhost_iov_iter *dst_it)
+			    struct rte_vhost_iovec *iovec,
+			    struct rte_vhost_iov_iter *iter)
 {
 	uint16_t nr_vec = 0;
 	uint16_t avail_idx = vq->last_avail_idx;
@@ -1757,8 +1747,7 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
 	}
 
 	if (unlikely(async_mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec,
-					*nr_buffers, src_iovec, dst_iovec,
-					src_it, dst_it) < 0))
+					*nr_buffers, iovec, iter) < 0))
 		return -1;
 
 	vhost_shadow_enqueue_packed(vq, buffer_len, buffer_buf_id, buffer_desc_count, *nr_buffers);
@@ -1769,14 +1758,12 @@ vhost_enqueue_async_packed(struct virtio_net *dev,
 static __rte_always_inline int16_t
 virtio_dev_rx_async_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			    struct rte_mbuf *pkt, uint16_t *nr_descs, uint16_t *nr_buffers,
-			    struct iovec *src_iovec, struct iovec *dst_iovec,
-			    struct rte_vhost_iov_iter *src_it, struct rte_vhost_iov_iter *dst_it)
+			    struct rte_vhost_iovec *iovec, struct rte_vhost_iov_iter *iter)
 {
 	struct buf_vector buf_vec[BUF_VECTOR_MAX];
 
 	if (unlikely(vhost_enqueue_async_packed(dev, vq, pkt, buf_vec, nr_descs, nr_buffers,
-						 src_iovec, dst_iovec,
-						 src_it, dst_it) < 0)) {
+						 iovec, iter) < 0)) {
 		VHOST_LOG_DATA(DEBUG, "(%d) failed to get enough desc from vring\n", dev->vid);
 		return -1;
 	}
@@ -1825,11 +1812,9 @@ virtio_dev_rx_async_submit_packed(struct virtio_net *dev,
 	uint16_t num_descs;
 
 	struct vhost_async *async = vq->async;
-	struct rte_vhost_iov_iter *src_iter = async->src_iov_iter;
-	struct rte_vhost_iov_iter *dst_iter = async->dst_iov_iter;
+	struct rte_vhost_iov_iter *iter = async->iov_iter;
 	struct rte_vhost_async_desc tdes[MAX_PKT_BURST];
-	struct iovec *src_iovec = async->src_iovec;
-	struct iovec *dst_iovec = async->dst_iovec;
+	struct rte_vhost_iovec *iovec = async->iovec;
 	struct async_inflight_info *pkts_info = async->pkts_info;
 	uint32_t n_pkts = 0, pkt_err = 0;
 	uint16_t slot_idx = 0;
@@ -1842,17 +1827,16 @@ virtio_dev_rx_async_submit_packed(struct virtio_net *dev,
 		num_descs = 0;
 		if (unlikely(virtio_dev_rx_async_packed(dev, vq, pkts[pkt_idx],
 						&num_descs, &num_buffers,
-						&src_iovec[iovec_idx], &dst_iovec[iovec_idx],
-						&src_iter[it_idx], &dst_iter[it_idx]) < 0))
+						&iovec[iovec_idx], &iter[it_idx]) < 0))
 			break;
 
 		slot_idx = (async->pkts_idx + pkt_idx) % vq->size;
 
-		async_fill_desc(&tdes[pkt_burst_idx++], &src_iter[it_idx], &dst_iter[it_idx]);
+		async_fill_desc(&tdes[pkt_burst_idx++], &iter[it_idx]);
 		pkts_info[slot_idx].descs = num_descs;
 		pkts_info[slot_idx].nr_buffers = num_buffers;
 		pkts_info[slot_idx].mbuf = pkts[pkt_idx];
-		iovec_idx += src_iter[it_idx].nr_segs;
+		iovec_idx += iter[it_idx].nr_segs;
 		it_idx++;
 
 		pkt_idx++;
-- 
2.31.1