Hi Balazs Nemeth, Your patch cause a bug about virtio-user can't recieve packets when use packed ring and ring size is 255.
Please have a look about it. https://bugs.dpdk.org/show_bug.cgi?id=699 Thanks. Regards, Ling Wei > -----Original Message----- > From: dev <dev-boun...@dpdk.org> On Behalf Of Balazs Nemeth > Sent: Wednesday, April 7, 2021 05:55 PM > To: bnem...@redhat.com; dev@dpdk.org > Subject: [dpdk-dev] [PATCH v3] vhost: read last used index once > > Instead of calculating the address of a packed descriptor based on the > vq->desc_packed and vq->last_used_idx every time, store that base > address in desc_base. On arm, this saves 176 bytes in code size of function in > which vhost_flush_enqueue_batch_packed gets inlined. > > Signed-off-by: Balazs Nemeth <bnem...@redhat.com> > --- > lib/librte_vhost/virtio_net.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c > index > 179c57b46..f091384a6 100644 > --- a/lib/librte_vhost/virtio_net.c > +++ b/lib/librte_vhost/virtio_net.c > @@ -217,6 +217,8 @@ vhost_flush_enqueue_batch_packed(struct > virtio_net *dev, { > uint16_t i; > uint16_t flags; > + uint16_t last_used_idx = vq->last_used_idx; > + struct vring_packed_desc *desc_base = &vq- > >desc_packed[last_used_idx]; > > if (vq->shadow_used_idx) { > do_data_copy_enqueue(dev, vq); > @@ -226,16 +228,17 @@ vhost_flush_enqueue_batch_packed(struct > virtio_net *dev, > flags = PACKED_DESC_ENQUEUE_USED_FLAG(vq- > >used_wrap_counter); > > vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) { > - vq->desc_packed[vq->last_used_idx + i].id = ids[i]; > - vq->desc_packed[vq->last_used_idx + i].len = lens[i]; > + desc_base[i].id = ids[i]; > + desc_base[i].len = lens[i]; > } > > rte_atomic_thread_fence(__ATOMIC_RELEASE); > > - vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) > - vq->desc_packed[vq->last_used_idx + i].flags = flags; > + vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) { > + desc_base[i].flags = flags; > + } > > - vhost_log_cache_used_vring(dev, vq, vq->last_used_idx * > + vhost_log_cache_used_vring(dev, vq, last_used_idx * > sizeof(struct vring_packed_desc), > sizeof(struct vring_packed_desc) * > PACKED_BATCH_SIZE); > -- > 2.30.2
