On 9/17/19 7:28 AM, Joyce Kong wrote: > In case VIRTIO_F_ORDER_PLATFORM(36) is not negotiated, then the frontend > and backend are assumed to be implemented in software, that is they can > run on identical CPUs in an SMP configuration. > Thus a weak form of memory barriers like rte_smp_r/wmb, other than > rte_cio_r/wmb, is sufficient for this case(vq->hw->weak_barriers == 1) > and yields better performance. > For the above case, this patch helps yielding even better performance > by replacing the two-way barriers with C11 one-way barriers for avail > flags in packed ring. > > Meanwhile, a read barrier is required to ensure ordering between > descriptor's flags and content reads[1]. With C11, load-acquire can > enforce the ordering instead of rmb barrier. > > [1]https://patchwork.dpdk.org/patch/49109/ > > Signed-off-by: Joyce Kong <joyce.k...@arm.com> > Reviewed-by: Gavin Hu <gavin...@arm.com> > Reviewed-by: Phil Yang <phil.y...@arm.com> > Reviewed-by: Maxime Coquelin <maxime.coque...@redhat.com> > --- > drivers/net/virtio/virtio_rxtx.c | 13 +++++++------ > drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 +++++- > drivers/net/virtio/virtqueue.h | 21 +++++++++++++++++++++ > lib/librte_vhost/vhost.h | 2 +- > lib/librte_vhost/virtio_net.c | 11 +++++------ > 5 files changed, 39 insertions(+), 14 deletions(-) > Reviewed-by: Maxime Coquelin <maxime.coque...@redhat.com> Thanks, Maxime
