On 04/06, 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
>index in split ring.
>
>Signed-off-by: Joyce Kong <joyce.k...@arm.com>
>Reviewed-by: Gavin Hu <gavin...@arm.com>
>---
> drivers/net/virtio/virtio_ethdev.c | 9 ++--
> drivers/net/virtio/virtio_ring.h | 2 +-
> drivers/net/virtio/virtio_rxtx.c | 46 +++++++++----------
> drivers/net/virtio/virtio_rxtx_simple_neon.c | 5 +-
> drivers/net/virtio/virtio_rxtx_simple_sse.c | 5 +-
> .../net/virtio/virtio_user/virtio_user_dev.c | 8 ++--
> drivers/net/virtio/virtqueue.c | 2 +-
> drivers/net/virtio/virtqueue.h | 37 ++++++++++++---
> lib/librte_vhost/virtio_net.c | 5 +-
> 9 files changed, 71 insertions(+), 48 deletions(-)
>
>diff --git a/drivers/net/virtio/virtio_ethdev.c
>b/drivers/net/virtio/virtio_ethdev.c
>index f9d0ea70d..a4a865bfa 100644
>--- a/drivers/net/virtio/virtio_ethdev.c
>+++ b/drivers/net/virtio/virtio_ethdev.c
>@@ -285,13 +285,12 @@ virtio_send_command_split(struct virtnet_ctl *cvq,
>
> virtqueue_notify(vq);
>
>- rte_rmb();
>- while (VIRTQUEUE_NUSED(vq) == 0) {
>- rte_rmb();
>+ /* virtqueue_nused has a load-acquire or rte_cio_rmb inside */
>+ while (virtqueue_nused(vq) == 0)
> usleep(100);
>- }
>
>- while (VIRTQUEUE_NUSED(vq)) {
>+ /* virtqueue_nused has a load-acquire or rte_cio_rmb inside */
>+ while (virtqueue_nused(vq)) {
> uint32_t idx, desc_idx, used_idx;
> struct vring_used_elem *uep;
>
>diff --git a/drivers/net/virtio/virtio_ring.h
>b/drivers/net/virtio/virtio_ring.h
>index 7ba34662e..0f6574f68 100644
>--- a/drivers/net/virtio/virtio_ring.h
>+++ b/drivers/net/virtio/virtio_ring.h
>@@ -59,7 +59,7 @@ struct vring_used_elem {
>
> struct vring_used {
> uint16_t flags;
>- volatile uint16_t idx;
>+ uint16_t idx;
> struct vring_used_elem ring[0];
> };
>
>diff --git a/drivers/net/virtio/virtio_rxtx.c
>b/drivers/net/virtio/virtio_rxtx.c
>index 752faa0f6..9ba26fd95 100644
>--- a/drivers/net/virtio/virtio_rxtx.c
>+++ b/drivers/net/virtio/virtio_rxtx.c
>@@ -45,7 +45,7 @@ virtio_dev_rx_queue_done(void *rxq, uint16_t offset)
> struct virtnet_rx *rxvq = rxq;
> struct virtqueue *vq = rxvq->vq;
>
>- return VIRTQUEUE_NUSED(vq) >= offset;
>+ return virtqueue_nused(vq) >= offset;
> }
>
> void
>@@ -1243,9 +1243,8 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf
>**rx_pkts, uint16_t nb_pkts)
> if (unlikely(hw->started == 0))
> return nb_rx;
>
>- nb_used = VIRTQUEUE_NUSED(vq);
>-
>- virtio_rmb(hw->weak_barriers);
>+ /* virtqueue_nused has a load-acquire or rte_cio_rmb inside */
Small nit, I don't think we need to add this comment to every occurrence of
virtqueue_nused, what about moving it to the definition of this function?
Thanks,
Xiaolong
