[dpdk-dev] [PATCH v5 5/6] vhost: batch update used ring
Maxime Coquelin
maxime.coquelin at redhat.com
Mon Sep 12 17:45:40 CEST 2016
On 09/09/2016 05:39 AM, Zhihong Wang wrote:
> This patch enables batch update of the used ring for better efficiency.
>
> Signed-off-by: Zhihong Wang <zhihong.wang at intel.com>
> ---
> Changes in v4:
>
> 1. Free shadow used ring in the right place.
>
> 2. Add failure check for shadow used ring malloc.
>
> lib/librte_vhost/vhost.c | 20 ++++++++++++--
> lib/librte_vhost/vhost.h | 4 +++
> lib/librte_vhost/vhost_user.c | 31 +++++++++++++++++----
> lib/librte_vhost/virtio_net.c | 64 +++++++++++++++++++++++++++++++++++--------
> 4 files changed, 101 insertions(+), 18 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> index 46095c3..cb31cdd 100644
> --- a/lib/librte_vhost/vhost.c
> +++ b/lib/librte_vhost/vhost.c
> @@ -119,10 +119,26 @@ cleanup_device(struct virtio_net *dev, int destroy)
> static void
> free_device(struct virtio_net *dev)
> {
> + struct vhost_virtqueue *vq_0;
> + struct vhost_virtqueue *vq_1;
> uint32_t i;
>
> - for (i = 0; i < dev->virt_qp_nb; i++)
> - rte_free(dev->virtqueue[i * VIRTIO_QNUM]);
> + for (i = 0; i < dev->virt_qp_nb; i++) {
> + vq_0 = dev->virtqueue[i * VIRTIO_QNUM];
> + if (vq_0->shadow_used_ring) {
> + rte_free(vq_0->shadow_used_ring);
> + vq_0->shadow_used_ring = NULL;
> + }
> +
> + vq_1 = dev->virtqueue[i * VIRTIO_QNUM + 1];
> + if (vq_1->shadow_used_ring) {
> + rte_free(vq_1->shadow_used_ring);
> + vq_1->shadow_used_ring = NULL;
> + }
> +
> + /* malloc together, free together */
> + rte_free(vq_0);
> + }
>
> rte_free(dev);
> }
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 9707dfc..381dc27 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -85,6 +85,10 @@ struct vhost_virtqueue {
>
> /* Physical address of used ring, for logging */
> uint64_t log_guest_addr;
> +
> + /* Shadow used ring for performance */
> + struct vring_used_elem *shadow_used_ring;
> + uint32_t shadow_used_idx;
> } __rte_cache_aligned;
>
> /* Old kernels have no such macro defined */
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index eee99e9..d7cf1ed 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -193,7 +193,21 @@ static int
> vhost_user_set_vring_num(struct virtio_net *dev,
> struct vhost_vring_state *state)
> {
> - dev->virtqueue[state->index]->size = state->num;
> + struct vhost_virtqueue *vq;
> +
> + vq = dev->virtqueue[state->index];
> + vq->size = state->num;
> + if (!vq->shadow_used_ring) {
> + vq->shadow_used_ring = rte_malloc(NULL,
> + vq->size * sizeof(struct vring_used_elem),
> + RTE_CACHE_LINE_SIZE);
> + if (!vq->shadow_used_ring) {
> + RTE_LOG(ERR, VHOST_CONFIG,
> + "Failed to allocate memory"
> + " for shadow used ring.\n");
> + return -1;
> + }
> + }
>
> return 0;
> }
> @@ -611,14 +625,21 @@ static int
> vhost_user_get_vring_base(struct virtio_net *dev,
> struct vhost_vring_state *state)
> {
> + struct vhost_virtqueue *vq;
> +
> /* We have to stop the queue (virtio) if it is running. */
> if (dev->flags & VIRTIO_DEV_RUNNING) {
> dev->flags &= ~VIRTIO_DEV_RUNNING;
> notify_ops->destroy_device(dev->vid);
> }
>
> + vq = dev->virtqueue[state->index];
> /* Here we are safe to get the last used index */
> - state->num = dev->virtqueue[state->index]->last_used_idx;
> + state->num = vq->last_used_idx;
> + if (vq->shadow_used_ring) {
> + rte_free(vq->shadow_used_ring);
> + vq->shadow_used_ring = NULL;
> + }
>
> RTE_LOG(INFO, VHOST_CONFIG,
> "vring base idx:%d file:%d\n", state->index, state->num);
> @@ -627,10 +648,10 @@ vhost_user_get_vring_base(struct virtio_net *dev,
> * sent and only sent in vhost_vring_stop.
> * TODO: cleanup the vring, it isn't usable since here.
> */
> - if (dev->virtqueue[state->index]->kickfd >= 0)
> - close(dev->virtqueue[state->index]->kickfd);
> + if (vq->kickfd >= 0)
> + close(vq->kickfd);
>
> - dev->virtqueue[state->index]->kickfd = VIRTIO_UNINITIALIZED_EVENTFD;
> + vq->kickfd = VIRTIO_UNINITIALIZED_EVENTFD;
>
> return 0;
> }
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index b38f18f..e9f6353 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -134,17 +134,52 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_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)
> +update_used_ring(struct vhost_virtqueue *vq, uint32_t desc_chain_head,
> + uint32_t desc_chain_len)
> {
> - uint32_t used_idx = vq->last_used_idx & (vq->size - 1);
> -
> - vq->used->ring[used_idx].id = desc_chain_head;
> - vq->used->ring[used_idx].len = desc_chain_len;
> + vq->shadow_used_ring[vq->shadow_used_idx].id = desc_chain_head;
> + vq->shadow_used_ring[vq->shadow_used_idx].len = desc_chain_len;
> + vq->shadow_used_idx++;
> vq->last_used_idx++;
> - vhost_log_used_vring(dev, vq, offsetof(struct vring_used,
> - ring[used_idx]),
> - sizeof(vq->used->ring[used_idx]));
> +}
> +
> +static inline void __attribute__((always_inline))
> +flush_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq,
> + uint32_t used_idx_start)
> +{
> + if (used_idx_start + vq->shadow_used_idx < vq->size) {
> + rte_memcpy(&vq->used->ring[used_idx_start],
> + &vq->shadow_used_ring[0],
> + vq->shadow_used_idx *
> + sizeof(struct vring_used_elem));
> + vhost_log_used_vring(dev, vq,
> + offsetof(struct vring_used,
> + ring[used_idx_start]),
> + vq->shadow_used_idx *
> + sizeof(struct vring_used_elem));
> + } else {
> + uint32_t part_1 = vq->size - used_idx_start;
> + uint32_t part_2 = vq->shadow_used_idx - part_1;
> +
> + rte_memcpy(&vq->used->ring[used_idx_start],
> + &vq->shadow_used_ring[0],
> + part_1 *
> + sizeof(struct vring_used_elem));
> + vhost_log_used_vring(dev, vq,
> + offsetof(struct vring_used,
> + ring[used_idx_start]),
> + part_1 *
> + sizeof(struct vring_used_elem));
> + rte_memcpy(&vq->used->ring[0],
> + &vq->shadow_used_ring[part_1],
> + part_2 *
> + sizeof(struct vring_used_elem));
> + vhost_log_used_vring(dev, vq,
> + offsetof(struct vring_used,
> + ring[0]),
> + part_2 *
> + sizeof(struct vring_used_elem));
> + }
> }
Is expanding the code done for performance purpose?
Or maybe we could have a loop to do that?
Something like this (not compiled, not tested):
static inline void __attribute__((always_inline))
flush_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq,
{
uint32_t to = used_idx_start;
uint32_t from = 0;
uint32_t count;
if (used_idx_start + vq->shadow_used_idx < vq->size)
count = vq->shadow_used_idx;
else
count = vq->size - used_idx_start;
do {
rte_memcpy(&vq->used->ring[to],
&vq->shadow_used_ring[from],
count * sizeof(struct vring_used_elem));
vhost_log_used_vring(dev, vq,
offsetof(struct vring_used, ring[to]),
count * sizeof(struct vring_used_elem));
to = (to + count) & (vq->size - 1);
from += count;
count = vq->shadow_used_idx - count;
} while (count);
}
Regards,
Maxime
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