The virtio ring in QEMU/KVM is usually limited to 256 entries
and the normal way that virtio driver was queuing mbufs required
nsegs + 1 ring elements. By using the indirect ring element feature
if available, each packet will take only one ring slot even for
multi-segment packets.
Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
drivers/net/virtio/virtio_ethdev.c | 11 +++++---
drivers/net/virtio/virtio_ethdev.h | 3 ++-
drivers/net/virtio/virtio_rxtx.c | 51 ++++++++++++++++++++++++++++++--------
drivers/net/virtio/virtqueue.h | 8 ++++++
4 files changed, 57 insertions(+), 16 deletions(-)
diff --git a/drivers/net/virtio/virtio_ethdev.c
b/drivers/net/virtio/virtio_ethdev.c
index 465d3cd..bcfb87b 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -359,12 +359,15 @@ int virtio_dev_queue_setup(struct rte_eth_dev *dev,
if (queue_type == VTNET_TQ) {
/*
* For each xmit packet, allocate a virtio_net_hdr
+ * and indirect ring elements
*/
snprintf(vq_name, sizeof(vq_name), "port%d_tvq%d_hdrzone",
- dev->data->port_id, queue_idx);
- vq->virtio_net_hdr_mz = rte_memzone_reserve_aligned(vq_name,
- vq_size * hw->vtnet_hdr_size,
- socket_id, 0, RTE_CACHE_LINE_SIZE);
+ dev->data->port_id, queue_idx);
+
+ vq->virtio_net_hdr_mz =
+ rte_memzone_reserve_aligned(vq_name,
+ vq_size * sizeof(struct
virtio_tx_region),
+ socket_id, 0,
RTE_CACHE_LINE_SIZE);
if (vq->virtio_net_hdr_mz == NULL) {
if (rte_errno == EEXIST)
vq->virtio_net_hdr_mz =
diff --git a/drivers/net/virtio/virtio_ethdev.h
b/drivers/net/virtio/virtio_ethdev.h
index 9026d42..07a9265 100644
--- a/drivers/net/virtio/virtio_ethdev.h
+++ b/drivers/net/virtio/virtio_ethdev.h
@@ -64,7 +64,8 @@
1u << VIRTIO_NET_F_CTRL_VQ | \
1u << VIRTIO_NET_F_CTRL_RX | \
1u << VIRTIO_NET_F_CTRL_VLAN | \
- 1u << VIRTIO_NET_F_MRG_RXBUF)
+ 1u << VIRTIO_NET_F_MRG_RXBUF | \
+ 1u << VIRTIO_RING_F_INDIRECT_DESC)
/*
* CQ function prototype
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index dbe6665..8979695 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -199,14 +199,15 @@ virtqueue_enqueue_recv_refill(struct virtqueue *vq,
struct rte_mbuf *cookie)
}
static int
-virtqueue_enqueue_xmit(struct virtqueue *txvq, struct rte_mbuf *cookie)
+virtqueue_enqueue_xmit(struct virtqueue *txvq, struct rte_mbuf *cookie,
+ int use_indirect)
{
struct vq_desc_extra *dxp;
struct vring_desc *start_dp;
uint16_t seg_num = cookie->nb_segs;
- uint16_t needed = 1 + seg_num;
+ uint16_t needed = use_indirect ? 1 : 1 + seg_num;
uint16_t head_idx, idx;
- uint16_t head_size = txvq->hw->vtnet_hdr_size;
+ unsigned long offs;
if (unlikely(txvq->vq_free_cnt == 0))
return -ENOSPC;
@@ -220,11 +221,26 @@ virtqueue_enqueue_xmit(struct virtqueue *txvq, struct
rte_mbuf *cookie)
dxp = &txvq->vq_descx[idx];
dxp->cookie = (void *)cookie;
dxp->ndescs = needed;
-
start_dp = txvq->vq_ring.desc;
- start_dp[idx].addr =
- txvq->virtio_net_hdr_mem + idx * head_size;
- start_dp[idx].len = (uint32_t)head_size;
+
+ if (use_indirect) {
+ offs = offsetof(struct virtio_tx_region, tx_indir)
+ + idx * sizeof(struct virtio_tx_region);
+
+ start_dp[idx].addr = txvq->virtio_net_hdr_mem + offs;
+ start_dp[idx].len = sizeof(struct vring_desc);
+ start_dp[idx].flags = VRING_DESC_F_INDIRECT;
+
+ start_dp = (struct vring_desc *)
+ ((char *)txvq->virtio_net_hdr_mz->addr + offs);
+ idx = 0;
+ }
+
+ offs = offsetof(struct virtio_tx_region, tx_hdr)
+ + idx * sizeof(struct virtio_tx_region);
+
+ start_dp[idx].addr = txvq->virtio_net_hdr_mem + offs;
+ start_dp[idx].len = txvq->hw->vtnet_hdr_size;
start_dp[idx].flags = VRING_DESC_F_NEXT;
for (; ((seg_num > 0) && (cookie != NULL)); seg_num--) {
@@ -236,7 +252,12 @@ virtqueue_enqueue_xmit(struct virtqueue *txvq, struct
rte_mbuf *cookie)
}
start_dp[idx].flags &= ~VRING_DESC_F_NEXT;
- idx = start_dp[idx].next;
+
+ if (use_indirect)
+ idx = txvq->vq_ring.desc[head_idx].next;
+ else
+ idx = start_dp[idx].next;
+
txvq->vq_desc_head_idx = idx;
if (txvq->vq_desc_head_idx == VQ_RING_DESC_CHAIN_END)
txvq->vq_desc_tail_idx = idx;
@@ -760,7 +781,15 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
**tx_pkts, uint16_t nb_pkts)
for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
struct rte_mbuf *txm = tx_pkts[nb_tx];
- int need = txm->nb_segs - txvq->vq_free_cnt + 1;
+ int use_indirect, slots, need;
+
+ use_indirect = vtpci_with_feature(txvq->hw,
+ VIRTIO_RING_F_INDIRECT_DESC)
+ && (txm->nb_segs < VIRTIO_MAX_TX_INDIRECT);
+
+ /* How many ring entries are needed to this Tx? */
+ slots = use_indirect ? 1 : 1 + txm->nb_segs;
+ need = slots - txvq->vq_free_cnt;
/* Positive value indicates it need free vring descriptors */
if (need > 0) {
@@ -769,7 +798,7 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
uint16_t nb_pkts)
need = RTE_MIN(need, (int)nb_used);
virtio_xmit_cleanup(txvq, need);
- need = txm->nb_segs - txvq->vq_free_cnt + 1;
+ need = slots - txvq->vq_free_cnt;
if (unlikely(need > 0)) {
PMD_TX_LOG(ERR,
"No free tx descriptors to
transmit");
@@ -787,7 +816,7 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
uint16_t nb_pkts)
}
/* Enqueue Packet buffers */
- error = virtqueue_enqueue_xmit(txvq, txm);
+ error = virtqueue_enqueue_xmit(txvq, txm, use_indirect);
if (unlikely(error)) {
if (error == ENOSPC)
PMD_TX_LOG(ERR, "virtqueue_enqueue Free count =
0");
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 7789411..a9410b4 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -237,6 +237,14 @@ struct virtio_net_hdr_mrg_rxbuf {
uint16_t num_buffers; /**< Number of merged rx buffers */
};
+/* Region reserved to allow for transmit header and indirect ring */
+#define VIRTIO_MAX_TX_INDIRECT 8
+struct virtio_tx_region {
+ struct virtio_net_hdr_mrg_rxbuf tx_hdr;
+ struct vring_desc tx_indir[VIRTIO_MAX_TX_INDIRECT]
+ __attribute__((__aligned__(16)));
+};
+
/**
* Tell the backend not to interrupt us.
*/
--
2.1.4
