Re: [dpdk-dev] [PATCH] vhost: do deep copy while reallocate vq

["Yang, Zhiyong" <zhiyong.yang@intel.com>]

> -----Original Message-----
> From: Chen, Junjie J
> Sent: Tuesday, January 16, 2018 3:39 PM
> To: Yang, Zhiyong <zhiyong.yang@intel.com>; yliu@fridaylinux.org;
> maxime.coquelin@redhat.com
> Cc: dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH] vhost: do deep copy while reallocate vq
> 
> Hi
> > > > > @@ -227,6 +227,7 @@ vhost_user_set_vring_num(struct virtio_net
> > *dev,
> > > > >  				"zero copy is force disabled\n");
> > > > >  			dev->dequeue_zero_copy = 0;
> > > > >  		}
> > > > > +		TAILQ_INIT(&vq->zmbuf_list);
> > > > >  	}
> > > > >
> > > > >  	vq->shadow_used_ring = rte_malloc(NULL, @@ -261,6
> +262,9
> > @@
> > > > > numa_realloc(struct virtio_net *dev, int index)
> > > > >  	int oldnode, newnode;
> > > > >  	struct virtio_net *old_dev;
> > > > >  	struct vhost_virtqueue *old_vq, *vq;
> > > > > +	struct zcopy_mbuf *new_zmbuf;
> > > > > +	struct vring_used_elem *new_shadow_used_ring;
> > > > > +	struct batch_copy_elem *new_batch_copy_elems;
> > > > >  	int ret;
> > > > >
> > > > >  	old_dev = dev;
> > > > > @@ -285,6 +289,33 @@ numa_realloc(struct virtio_net *dev, int
> > index)
> > > > >  			return dev;
> > > > >
> > > > >  		memcpy(vq, old_vq, sizeof(*vq));
> > > > > +		TAILQ_INIT(&vq->zmbuf_list);
> > > > > +
> > > > > +		new_zmbuf = rte_malloc_socket(NULL, vq-
> >zmbuf_size *
> > > > > +			sizeof(struct zcopy_mbuf), 0, newnode);
> > > > > +		if (new_zmbuf) {
> > > > > +			rte_free(vq->zmbufs);
> > > > > +			vq->zmbufs = new_zmbuf;
> > > > > +		}
> > > >
> > > > You need to consider how to handle the case  ( rte_malloc_socket
> > > > return NULL).
> > >
> > > If it failed to allocate new_zmbuf, it uses old zmbufs, so as to
> > > keep vhost alive.
> >
> > It sounds reasonable, another question is, for the 3 blocks of memory
> > being allocated,  If some succeed , others fails,  Does it mean that
> > the code will run on different socket?  What's the perf impact if it happens.
> 
> The original code doesn't do deep copy and thus access memory on different
> socket, this patch is to mitigate this situation. It does access remote memory
> when one of above allocation failed.
> 
> I saw some performance improvement (24.8Gbits/s -> 26.1Gbit/s) on my dev
> machine when only reallocate for zmbufs, while I didn't see significant
> performance difference when allocating vring_used_elem and
> batch_copy_elem.

Great, 

Reviewed-by: Zhiyong Yang <zhiyong.yang@intel.com> 

Thanks
Zhiyong