> -----Original Message-----
> From: Liu, Yong
> Sent: Wednesday, September 25, 2019 1:38 PM
> To: Gavin Hu (Arm Technology China) <gavin...@arm.com>;
> maxime.coque...@redhat.com; Bie, Tiwei <tiwei....@intel.com>; Wang, Zhihong
> <zhihong.w...@intel.com>
> Cc: dev@dpdk.org; nd <n...@arm.com>
> Subject: RE: [dpdk-dev] [PATCH v2 08/16] vhost: add flush function for
> burst enqueue
>
>
>
> > -----Original Message-----
> > From: Gavin Hu (Arm Technology China) [mailto:gavin...@arm.com]
> > Sent: Wednesday, September 25, 2019 11:38 AM
> > To: Liu, Yong <yong....@intel.com>; maxime.coque...@redhat.com; Bie,
> Tiwei
> > <tiwei....@intel.com>; Wang, Zhihong <zhihong.w...@intel.com>
> > Cc: dev@dpdk.org; nd <n...@arm.com>
> > Subject: RE: [dpdk-dev] [PATCH v2 08/16] vhost: add flush function for
> > burst enqueue
> >
> > Hi Marvin,
> >
> > One typo and one comment about the barrier.
> >
> > /Gavin
> >
> > > -----Original Message-----
> > > From: dev <dev-boun...@dpdk.org> On Behalf Of Marvin Liu
> > > Sent: Friday, September 20, 2019 12:37 AM
> > > To: maxime.coque...@redhat.com; tiwei....@intel.com;
> > > zhihong.w...@intel.com
> > > Cc: dev@dpdk.org; Marvin Liu <yong....@intel.com>
> > > Subject: [dpdk-dev] [PATCH v2 08/16] vhost: add flush function for
> burst
> > > enqueue
> > >
> > > Flush used flags when burst enqueue function is finished. Descriptor's
> > > flags are pre-calculated as them will be reset by vhost.
> > s/them/they
> >
>
> Thanks.
>
> > >
> > > Signed-off-by: Marvin Liu <yong....@intel.com>
> > >
> > > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> > > index 000648dd4..9c42c7db0 100644
> > > --- a/lib/librte_vhost/vhost.h
> > > +++ b/lib/librte_vhost/vhost.h
> > > @@ -39,6 +39,9 @@
> > >
> > > #define VHOST_LOG_CACHE_NR 32
> > >
> > > +#define VIRTIO_RX_USED_FLAG (0ULL | VRING_DESC_F_AVAIL |
> > > VRING_DESC_F_USED \
> > > + | VRING_DESC_F_WRITE)
> > > +#define VIRTIO_RX_USED_WRAP_FLAG (VRING_DESC_F_WRITE)
> > > #define PACKED_DESCS_BURST (RTE_CACHE_LINE_SIZE / \
> > > sizeof(struct vring_packed_desc))
> > >
> > > diff --git a/lib/librte_vhost/virtio_net.c
> > b/lib/librte_vhost/virtio_net.c
> > > index e2787b72e..8e4036204 100644
> > > --- a/lib/librte_vhost/virtio_net.c
> > > +++ b/lib/librte_vhost/virtio_net.c
> > > @@ -169,6 +169,51 @@ update_shadow_packed(struct vhost_virtqueue
> > > *vq,
> > > vq->shadow_used_packed[i].count = count;
> > > }
> > >
> > > +static __rte_always_inline void
> > > +flush_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
> > > + uint64_t *lens, uint16_t *ids, uint16_t flags)
> > > +{
> > > + uint16_t i;
> > > +
> > > + UNROLL_PRAGMA(PRAGMA_PARAM)
> > > + for (i = 0; i < PACKED_DESCS_BURST; i++) {
> > > + vq->desc_packed[vq->last_used_idx + i].id = ids[i];
> > > + vq->desc_packed[vq->last_used_idx + i].len = lens[i];
> > > + }
> > > +
> > > + UNROLL_PRAGMA(PRAGMA_PARAM)
> > > + for (i = 0; i < PACKED_DESCS_BURST; i++) {
> > > + rte_smp_wmb();
> > Should this rte_smp_wmb() be moved above the loop? It guarantees the
> > orderings of updates of id, len happens before the flags,
> > But all the flags of different descriptors should not be ordered.
> >
> Hi Gavin,
> For each descriptor, virtio driver will first check flags and then check
> read barrier, at the last driver will read id and length.
> So wmb here is to guarantee that id and length are updated before flags.
> And afterwards wmb is to guarantee the sequence.
>
Gavin,
Checked with master branch, flags store sequence is not needed.
But in my environment, performance will be a litter better if ordered flags
store.
I think it may be harmless to place wmb here. How about your idea?
> Thanks,
> Marvin
>
> > > + vq->desc_packed[vq->last_used_idx + i].flags = flags;
> > > + }
> > > +
> > > + vhost_log_cache_used_vring(dev, vq, vq->last_used_idx *
> > > + sizeof(struct vring_packed_desc),
> > > + sizeof(struct vring_packed_desc) *
> > > + PACKED_DESCS_BURST);
> > > + vhost_log_cache_sync(dev, vq);
> > > +
> > > + vq->last_used_idx += PACKED_DESCS_BURST;
> > > + if (vq->last_used_idx >= vq->size) {
> > > + vq->used_wrap_counter ^= 1;
> > > + vq->last_used_idx -= vq->size;
> > > + }
> > > +}
> > > +
> > > +static __rte_always_inline void
> > > +flush_enqueue_burst_packed(struct virtio_net *dev, struct
> > > vhost_virtqueue *vq,
> > > + uint64_t *lens, uint16_t *ids)
> > > +{
> > > + uint16_t flags = 0;
> > > +
> > > + if (vq->used_wrap_counter)
> > > + flags = VIRTIO_RX_USED_FLAG;
> > > + else
> > > + flags = VIRTIO_RX_USED_WRAP_FLAG;
> > > +
> > > + flush_burst_packed(dev, vq, lens, ids, flags);
> > > +}
> > > +
> > > static __rte_always_inline void
> > > update_enqueue_shadow_packed(struct vhost_virtqueue *vq, uint16_t
> > > desc_idx,
> > > uint32_t len, uint16_t count)
> > > @@ -950,6 +995,7 @@ virtio_dev_rx_burst_packed(struct virtio_net *dev,
> > > struct vhost_virtqueue *vq,
> > > struct virtio_net_hdr_mrg_rxbuf *hdrs[PACKED_DESCS_BURST];
> > > uint32_t buf_offset = dev->vhost_hlen;
> > > uint64_t lens[PACKED_DESCS_BURST];
> > > + uint16_t ids[PACKED_DESCS_BURST];
> > >
> > > uint16_t i;
> > >
> > > @@ -1013,6 +1059,12 @@ virtio_dev_rx_burst_packed(struct virtio_net
> > > *dev, struct vhost_virtqueue *vq,
> > > pkts[i]->pkt_len);
> > > }
> > >
> > > + UNROLL_PRAGMA(PRAGMA_PARAM)
> > > + for (i = 0; i < PACKED_DESCS_BURST; i++)
> > > + ids[i] = descs[avail_idx + i].id;
> > > +
> > > + flush_enqueue_burst_packed(dev, vq, lens, ids);
> > > +
> > > return 0;
> > > }
> > >
> > > --
> > > 2.17.1
