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From: "Ouyang, Changchun" <changchun.ouyang@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>, "Xie, Huawei"
<huawei.xie@intel.com>
Thread-Topic: [PATCH 3/4] virtio: use indirect ring elements
Thread-Index: AQHQ51TG5SiLKqn2L0KGjDKr+OzoSZ4vLHow
Date: Sun, 6 Sep 2015 08:36:10 +0000
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Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 3/4] virtio: use indirect ring elements
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> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Saturday, September 5, 2015 4:58 AM
> To: Xie, Huawei; Ouyang, Changchun
> Cc: dev@dpdk.org; Stephen Hemminger
> Subject: [PATCH 3/4] virtio: use indirect ring elements
>=20
> The virtio ring in QEMU/KVM is usually limited to 256 entries and the nor=
mal
> 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.
>=20
> Signed-off-by: Stephen Hemminger <stephen@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(-)
>=20
> 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 =3D=3D VTNET_TQ) {
Do we also need implement indirect ring elements for RX path?
> /*
> * 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 =3D
> 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 =3D
> + 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 =3D=3D NULL) {
> if (rte_errno =3D=3D EEXIST)
> vq->virtio_net_hdr_mz =3D
> 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)
>=20
> /*
> * 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) }
>=20
> 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 =3D cookie->nb_segs;
> - uint16_t needed =3D 1 + seg_num;
> + uint16_t needed =3D use_indirect ? 1 : 1 + seg_num;
Do we need check if seg_num > VIRTIO_MAX_TX_INDIRECT?
That mean one slot is not enough for the whole big packet even it is indire=
ct ring.
> uint16_t head_idx, idx;
> - uint16_t head_size =3D txvq->hw->vtnet_hdr_size;
> + unsigned long offs;
>=20
> if (unlikely(txvq->vq_free_cnt =3D=3D 0))
> return -ENOSPC;
> @@ -220,11 +221,26 @@ virtqueue_enqueue_xmit(struct virtqueue *txvq,
> struct rte_mbuf *cookie)
> dxp =3D &txvq->vq_descx[idx];
> dxp->cookie =3D (void *)cookie;
> dxp->ndescs =3D needed;
> -
> start_dp =3D txvq->vq_ring.desc;
> - start_dp[idx].addr =3D
> - txvq->virtio_net_hdr_mem + idx * head_size;
> - start_dp[idx].len =3D (uint32_t)head_size;
> +
> + if (use_indirect) {
> + offs =3D offsetof(struct virtio_tx_region, tx_indir)
> + + idx * sizeof(struct virtio_tx_region);
> +
> + start_dp[idx].addr =3D txvq->virtio_net_hdr_mem + offs;
> + start_dp[idx].len =3D sizeof(struct vring_desc);
> + start_dp[idx].flags =3D VRING_DESC_F_INDIRECT;
> +
> + start_dp =3D (struct vring_desc *)
> + ((char *)txvq->virtio_net_hdr_mz->addr + offs);
> + idx =3D 0;
> + }
> +
> + offs =3D offsetof(struct virtio_tx_region, tx_hdr)
> + + idx * sizeof(struct virtio_tx_region);
> +
> + start_dp[idx].addr =3D txvq->virtio_net_hdr_mem + offs;
> + start_dp[idx].len =3D txvq->hw->vtnet_hdr_size;
> start_dp[idx].flags =3D VRING_DESC_F_NEXT;
>=20
> for (; ((seg_num > 0) && (cookie !=3D NULL)); seg_num--) { @@ -236,7
> +252,12 @@ virtqueue_enqueue_xmit(struct virtqueue *txvq, struct
> rte_mbuf *cookie)
> }
>=20
> start_dp[idx].flags &=3D ~VRING_DESC_F_NEXT;
> - idx =3D start_dp[idx].next;
> +
> + if (use_indirect)
> + idx =3D txvq->vq_ring.desc[head_idx].next;
> + else
> + idx =3D start_dp[idx].next;
> +
> txvq->vq_desc_head_idx =3D idx;
> if (txvq->vq_desc_head_idx =3D=3D VQ_RING_DESC_CHAIN_END)
> txvq->vq_desc_tail_idx =3D idx;
> @@ -760,7 +781,15 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf
> **tx_pkts, uint16_t nb_pkts)
>=20
> for (nb_tx =3D 0; nb_tx < nb_pkts; nb_tx++) {
> struct rte_mbuf *txm =3D tx_pkts[nb_tx];
> - int need =3D txm->nb_segs - txvq->vq_free_cnt + 1;
> + int use_indirect, slots, need;
> +
> + use_indirect =3D 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 =3D use_indirect ? 1 : 1 + txm->nb_segs;
> + need =3D slots - txvq->vq_free_cnt;
>=20
> /* 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 =3D RTE_MIN(need, (int)nb_used);
>=20
> virtio_xmit_cleanup(txvq, need);
> - need =3D txm->nb_segs - txvq->vq_free_cnt + 1;
> + need =3D 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)
> }
>=20
> /* Enqueue Packet buffers */
> - error =3D virtqueue_enqueue_xmit(txvq, txm);
> + error =3D virtqueue_enqueue_xmit(txvq, txm, use_indirect);
> if (unlikely(error)) {
> if (error =3D=3D ENOSPC)
> PMD_TX_LOG(ERR, "virtqueue_enqueue
> Free count =3D 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 */ };
>=20
> +/* 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