diff mbox

[dpdk-dev,v3,4/5] vhost: batch update used ring

Message ID 1471585430-125925-5-git-send-email-zhihong.wang@intel.com (mailing list archive)
State Superseded, archived
Delegated to: Yuanhan Liu
Headers show

Commit Message

Zhihong Wang Aug. 19, 2016, 5:43 a.m. UTC
This patch enables batch update of the used ring for better efficiency.

Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
---
 lib/librte_vhost/vhost-net.h  |  4 +++
 lib/librte_vhost/vhost_rxtx.c | 68 +++++++++++++++++++++++++++++++++----------
 lib/librte_vhost/virtio-net.c | 15 ++++++++--
 3 files changed, 68 insertions(+), 19 deletions(-)

Comments

Yuanhan Liu Aug. 25, 2016, 3:48 a.m. UTC | #1
On Fri, Aug 19, 2016 at 01:43:49AM -0400, Zhihong Wang wrote:
> This patch enables batch update of the used ring for better efficiency.
> 
> Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
...
> diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
> index 1785695..87d09fa 100644
> --- a/lib/librte_vhost/virtio-net.c
> +++ b/lib/librte_vhost/virtio-net.c
> @@ -152,10 +152,14 @@ cleanup_device(struct virtio_net *dev, int destroy)
>  static void
>  free_device(struct virtio_net *dev)
>  {
> +	struct vhost_virtqueue *vq;
>  	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 = dev->virtqueue[i * VIRTIO_QNUM];
> +		rte_free(vq->shadow_used_ring);
> +		rte_free(vq);
> +	}
>  	rte_free(dev);
>  }
> @@ -418,13 +422,18 @@ int
>  vhost_set_vring_num(int vid, struct vhost_vring_state *state)
>  {
>  	struct virtio_net *dev;
> +	struct vhost_virtqueue *vq;
>  
>  	dev = get_device(vid);
>  	if (dev == NULL)
>  		return -1;
>  
>  	/* State->index refers to the queue index. The txq is 1, rxq is 0. */
> -	dev->virtqueue[state->index]->size = state->num;
> +	vq = dev->virtqueue[state->index];
> +	vq->size = state->num;
> +	vq->shadow_used_ring = rte_malloc("",
> +			vq->size * sizeof(struct vring_used_elem),
> +			RTE_CACHE_LINE_SIZE);

Few notes here:

- I think the typical way to not specific a string type is using NULL,
  but not "".

- You should check the return value of rte_malloc: it could fail.

- Note that free_device() is invoked only when the vhost-user connection
  is broken (say the guest is halt). However, vhost_set_vring_num() could
  be invoked many times for a connection, say when you restart testpmd
  many times. This would lead to memory leak.

  The right way is to free it on get_vring_base().

	--yliu
Zhihong Wang Aug. 25, 2016, 5:19 a.m. UTC | #2
> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Thursday, August 25, 2016 11:48 AM
> To: Wang, Zhihong <zhihong.wang@intel.com>
> Cc: dev@dpdk.org; maxime.coquelin@redhat.com
> Subject: Re: [PATCH v3 4/5] vhost: batch update used ring
> 
> On Fri, Aug 19, 2016 at 01:43:49AM -0400, Zhihong Wang wrote:
> > This patch enables batch update of the used ring for better efficiency.
> >
> > Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
> ...
> > diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
> > index 1785695..87d09fa 100644
> > --- a/lib/librte_vhost/virtio-net.c
> > +++ b/lib/librte_vhost/virtio-net.c
> > @@ -152,10 +152,14 @@ cleanup_device(struct virtio_net *dev, int
> destroy)
> >  static void
> >  free_device(struct virtio_net *dev)
> >  {
> > +	struct vhost_virtqueue *vq;
> >  	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 = dev->virtqueue[i * VIRTIO_QNUM];
> > +		rte_free(vq->shadow_used_ring);
> > +		rte_free(vq);
> > +	}
> >  	rte_free(dev);
> >  }
> > @@ -418,13 +422,18 @@ int
> >  vhost_set_vring_num(int vid, struct vhost_vring_state *state)
> >  {
> >  	struct virtio_net *dev;
> > +	struct vhost_virtqueue *vq;
> >
> >  	dev = get_device(vid);
> >  	if (dev == NULL)
> >  		return -1;
> >
> >  	/* State->index refers to the queue index. The txq is 1, rxq is 0. */
> > -	dev->virtqueue[state->index]->size = state->num;
> > +	vq = dev->virtqueue[state->index];
> > +	vq->size = state->num;
> > +	vq->shadow_used_ring = rte_malloc("",
> > +			vq->size * sizeof(struct vring_used_elem),
> > +			RTE_CACHE_LINE_SIZE);
> 
> Few notes here:
> 
> - I think the typical way to not specific a string type is using NULL,
>   but not "".
> 
> - You should check the return value of rte_malloc: it could fail.
> 
> - Note that free_device() is invoked only when the vhost-user connection
>   is broken (say the guest is halt). However, vhost_set_vring_num() could
>   be invoked many times for a connection, say when you restart testpmd
>   many times. This would lead to memory leak.
> 
>   The right way is to free it on get_vring_base().

Good catch! Thanks.

> 
> 	--yliu
diff mbox

Patch

diff --git a/lib/librte_vhost/vhost-net.h b/lib/librte_vhost/vhost-net.h
index 51fdf3d..a15182c 100644
--- a/lib/librte_vhost/vhost-net.h
+++ b/lib/librte_vhost/vhost-net.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_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 7523b2d..c4abaf1 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -155,7 +155,6 @@  enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	uint32_t mbuf_avail = 0;
 	uint32_t copy_len = 0;
 	uint32_t extra_buffers = 0;
-	uint32_t used_idx_round = 0;
 
 	/* start with the first mbuf of the packet */
 	mbuf_len = rte_pktmbuf_data_len(mbuf);
@@ -203,17 +202,11 @@  enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq,
 					goto rollback;
 			} else if (is_mrg_rxbuf) {
 				/* start with the next desc chain */
-				used_idx_round = vq->last_used_idx
-					& (vq->size - 1);
-				vq->used->ring[used_idx_round].id =
+				vq->shadow_used_ring[vq->shadow_used_idx].id =
 					desc_chain_head;
-				vq->used->ring[used_idx_round].len =
+				vq->shadow_used_ring[vq->shadow_used_idx].len =
 					desc_chain_len;
-				vhost_log_used_vring(dev, vq,
-					offsetof(struct vring_used,
-						ring[used_idx_round]),
-					sizeof(vq->used->ring[
-						used_idx_round]));
+				vq->shadow_used_idx++;
 				vq->last_used_idx++;
 				extra_buffers++;
 				virtio_hdr->num_buffers++;
@@ -248,12 +241,9 @@  enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		desc_chain_len += copy_len;
 	}
 
-	used_idx_round = vq->last_used_idx & (vq->size - 1);
-	vq->used->ring[used_idx_round].id = desc_chain_head;
-	vq->used->ring[used_idx_round].len = desc_chain_len;
-	vhost_log_used_vring(dev, vq,
-		offsetof(struct vring_used, ring[used_idx_round]),
-		sizeof(vq->used->ring[used_idx_round]));
+	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++;
 
 	return 0;
@@ -268,6 +258,45 @@  error:
 }
 
 static inline void __attribute__((always_inline))
+update_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));
+	}
+}
+
+static inline void __attribute__((always_inline))
 notify_guest(struct virtio_net *dev, struct vhost_virtqueue *vq)
 {
 	rte_smp_wmb();
@@ -286,6 +315,7 @@  rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
 {
 	struct vhost_virtqueue *vq;
 	struct virtio_net *dev;
+	uint32_t used_idx_start = 0;
 	uint32_t pkt_idx = 0;
 	uint32_t pkt_left = 0;
 	uint32_t pkt_sent = 0;
@@ -315,6 +345,8 @@  rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
 	/* start enqueuing packets 1 by 1 */
 	pkt_idx = 0;
 	pkt_left = count;
+	vq->shadow_used_idx = 0;
+	used_idx_start = vq->last_used_idx & (vq->size - 1);
 	avail_idx = *((volatile uint16_t *)&vq->avail->idx);
 	while (1) {
 		if (loop_check(vq, avail_idx, pkt_left))
@@ -329,6 +361,10 @@  rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
 		pkt_left--;
 	}
 
+	/* batch update used ring for better performance */
+	if (likely(vq->shadow_used_idx > 0))
+		update_used_ring(dev, vq, used_idx_start);
+
 	/* update used idx and kick the guest if necessary */
 	if (pkt_sent)
 		notify_guest(dev, vq);
diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
index 1785695..87d09fa 100644
--- a/lib/librte_vhost/virtio-net.c
+++ b/lib/librte_vhost/virtio-net.c
@@ -152,10 +152,14 @@  cleanup_device(struct virtio_net *dev, int destroy)
 static void
 free_device(struct virtio_net *dev)
 {
+	struct vhost_virtqueue *vq;
 	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 = dev->virtqueue[i * VIRTIO_QNUM];
+		rte_free(vq->shadow_used_ring);
+		rte_free(vq);
+	}
 
 	rte_free(dev);
 }
@@ -418,13 +422,18 @@  int
 vhost_set_vring_num(int vid, struct vhost_vring_state *state)
 {
 	struct virtio_net *dev;
+	struct vhost_virtqueue *vq;
 
 	dev = get_device(vid);
 	if (dev == NULL)
 		return -1;
 
 	/* State->index refers to the queue index. The txq is 1, rxq is 0. */
-	dev->virtqueue[state->index]->size = state->num;
+	vq = dev->virtqueue[state->index];
+	vq->size = state->num;
+	vq->shadow_used_ring = rte_malloc("",
+			vq->size * sizeof(struct vring_used_elem),
+			RTE_CACHE_LINE_SIZE);
 
 	return 0;
 }