From: Yuanhan Liu Date: Sun, 9 Oct 2016 07:27:56 +0000 (+0800) Subject: vhost: introduce last available index for dequeue X-Git-Tag: spdx-start~5622 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=f6be82d7259ee35683721092d61283d99a47aff1;p=dpdk.git vhost: introduce last available index for dequeue So far, we retrieve both the used ring and avail ring idx by the var last_used_idx; it won't be a problem because the used ring is updated immediately after those avail entries are consumed. But that's not true when dequeue zero copy is enabled, that used ring is updated only when the mbuf is consumed. Thus, we need use another var to note the last avail ring idx we have consumed. Therefore, last_avail_idx is introduced. Signed-off-by: Yuanhan Liu Reviewed-by: Maxime Coquelin Tested-by: Qian Xu --- diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h index 2d5298745f..8565fa1c19 100644 --- a/lib/librte_vhost/vhost.h +++ b/lib/librte_vhost/vhost.h @@ -70,7 +70,7 @@ struct vhost_virtqueue { struct vring_used *used; uint32_t size; - /* Last index used on the available ring */ + uint16_t last_avail_idx; volatile uint16_t last_used_idx; #define VIRTIO_INVALID_EVENTFD (-1) #define VIRTIO_UNINITIALIZED_EVENTFD (-2) diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c index e651912c52..a92377a5a3 100644 --- a/lib/librte_vhost/vhost_user.c +++ b/lib/librte_vhost/vhost_user.c @@ -343,7 +343,8 @@ vhost_user_set_vring_addr(struct virtio_net *dev, struct vhost_vring_addr *addr) "last_used_idx (%u) and vq->used->idx (%u) mismatches; " "some packets maybe resent for Tx and dropped for Rx\n", vq->last_used_idx, vq->used->idx); - vq->last_used_idx = vq->used->idx; + vq->last_used_idx = vq->used->idx; + vq->last_avail_idx = vq->used->idx; } vq->log_guest_addr = addr->log_guest_addr; @@ -367,7 +368,8 @@ static int vhost_user_set_vring_base(struct virtio_net *dev, struct vhost_vring_state *state) { - dev->virtqueue[state->index]->last_used_idx = state->num; + dev->virtqueue[state->index]->last_used_idx = state->num; + dev->virtqueue[state->index]->last_avail_idx = state->num; return 0; } diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c index a59c39bb94..70301a5838 100644 --- a/lib/librte_vhost/virtio_net.c +++ b/lib/librte_vhost/virtio_net.c @@ -851,16 +851,17 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id, } } - avail_idx = *((volatile uint16_t *)&vq->avail->idx); - free_entries = avail_idx - vq->last_used_idx; + free_entries = *((volatile uint16_t *)&vq->avail->idx) - + vq->last_avail_idx; if (free_entries == 0) goto out; LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__); - /* Prefetch available ring to retrieve head indexes. */ - used_idx = vq->last_used_idx & (vq->size - 1); - rte_prefetch0(&vq->avail->ring[used_idx]); + /* Prefetch available and used ring */ + avail_idx = vq->last_avail_idx & (vq->size - 1); + used_idx = vq->last_used_idx & (vq->size - 1); + rte_prefetch0(&vq->avail->ring[avail_idx]); rte_prefetch0(&vq->used->ring[used_idx]); count = RTE_MIN(count, MAX_PKT_BURST); @@ -870,8 +871,9 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id, /* Retrieve all of the head indexes first to avoid caching issues. */ for (i = 0; i < count; i++) { - used_idx = (vq->last_used_idx + i) & (vq->size - 1); - desc_indexes[i] = vq->avail->ring[used_idx]; + avail_idx = (vq->last_avail_idx + i) & (vq->size - 1); + used_idx = (vq->last_used_idx + i) & (vq->size - 1); + desc_indexes[i] = vq->avail->ring[avail_idx]; vq->used->ring[used_idx].id = desc_indexes[i]; vq->used->ring[used_idx].len = 0; @@ -921,7 +923,8 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id, rte_smp_wmb(); rte_smp_rmb(); vq->used->idx += i; - vq->last_used_idx += i; + vq->last_avail_idx += i; + vq->last_used_idx += i; vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx), sizeof(vq->used->idx));