On 09/14/2016 10:43 AM, Wang, Zhihong wrote:
>
>
>> -----Original Message-----
>> From: Maxime Coquelin [mailto:maxime.coquelin at redhat.com]
>> Sent: Monday, September 12, 2016 11:46 PM
>> To: Wang, Zhihong <zhihong.wang at intel.com>; dev at dpdk.org
>> Cc: yuanhan.liu at linux.intel.com; thomas.monjalon at 6wind.com
>> Subject: Re: [PATCH v5 5/6] vhost: batch update used ring
>>
>>
>>
>> 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?
>
> Hi Maxime,
>
> Yes theoretically this has the least branch number.
> And I think the logic is simpler this way.
Ok, in that case, maybe you could create a function to
do the rte_memcpy and the vhost_log_used on a given range.
I don't have a strong opinion on this, if Yuanhan is fine
with current code, that's ok for me.
Thanks,
Maxime
>
> Thanks
> Zhihong
>
>> 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
