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

Wang, Zhihong zhihong.wang at intel.com
Thu Aug 25 07:19:07 CEST 2016



> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com]
> Sent: Thursday, August 25, 2016 11:48 AM
> To: Wang, Zhihong <zhihong.wang at intel.com>
> Cc: dev at dpdk.org; maxime.coquelin at 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 at 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


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