[dpdk-dev] [PATCH v3 2/2] virtio: one way barrier for packed vring desc used flags

[Maxime Coquelin]

On 9/9/19 11:14 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 used
> flags in packed ring.
> 
> Signed-off-by: Joyce Kong <joyce.kong at arm.com>
> Reviewed-by: Gavin Hu <gavin.hu at arm.com>
> Reviewed-by: Phil Yang <phil.yang at arm.com>
> ---
>  drivers/net/virtio/virtio_rxtx.c                 | 12 +++++++++---
>  drivers/net/virtio/virtio_user/virtio_user_dev.c |  4 ++--
>  drivers/net/virtio/virtqueue.h                   | 17 ++++++++++++++++-
>  lib/librte_vhost/virtio_net.c                    |  5 ++---
>  4 files changed, 29 insertions(+), 9 deletions(-)

Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>

Thanks,
Maxime