On 3/18/2016 6:39 PM, Ilya Maximets wrote: > > On 18.03.2016 13:27, Xie, Huawei wrote: >> On 3/18/2016 6:23 PM, Ilya Maximets wrote: >>> On 18.03.2016 13:08, Xie, Huawei wrote: >>>> On 2/24/2016 7:47 PM, Ilya Maximets wrote: >>>>> * Wait until it's our turn to add our buffer >>>>> @@ -979,7 +979,7 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, >>>>> uint16_t queue_id, >>>>> entry_success++; >>>>> } >>>>> >>>>> - rte_compiler_barrier(); >>>>> + rte_smp_rmb(); >>>> smp_rmb()? >>> There is no such function 'smp_rmb' in DPDK. >>> But: >>> .../arch/arm/rte_atomic.h:#define rte_smp_rmb() rte_rmb() >>> .../arch/ppc_64/rte_atomic.h:#define rte_smp_rmb() rte_compiler_barrier() >>> .../arch/tile/rte_atomic.h:#define rte_smp_rmb() rte_compiler_barrier() >>> .../arch/x86/rte_atomic.h:#define rte_smp_rmb() rte_compiler_barrier() >> I mean shoudn't be rte_smp_wmb()? > No. Here we need to be sure that copying of data from descriptor to > our local mbuf completed before 'vq->used->idx += entry_success;'. > > Read memory barrier will help us with it. > > In other places write barriers used because copying performed in > opposite direction.
What about the udpate to the used ring? > >>>>> vq->used->idx += entry_success; >>>>> vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx), >>>>> sizeof(vq->used->idx)); >>>>> -- 2.5.0 >>>> >> >>
