[07/17] examples/vhost: use previous value atomic fetch operations

  Use __atomic_fetch_{add,and,or,sub,xor} instead of
__atomic_{add,and,or,sub,xor}_fetch when we have no interest in the
result of the operation.

Reduces unnecessary codegen that provided the result of the atomic
operation that was not used.

Change brings closer alignment with atomics available in C11 standard
and will reduce review effort when they are integrated.

Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
 examples/vhost/main.c       | 12 ++++++------
 examples/vhost/virtio_net.c |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)
  

On 3/2/23 01:47, Tyler Retzlaff wrote:
> Use __atomic_fetch_{add,and,or,sub,xor} instead of
> __atomic_{add,and,or,sub,xor}_fetch when we have no interest in the
> result of the operation.
> 
> Reduces unnecessary codegen that provided the result of the atomic
> operation that was not used.
> 
> Change brings closer alignment with atomics available in C11 standard
> and will reduce review effort when they are integrated.
> 
> Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> ---
>   examples/vhost/main.c       | 12 ++++++------
>   examples/vhost/virtio_net.c |  4 ++--
>   2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/examples/vhost/main.c b/examples/vhost/main.c
> index 42e53a0..bfe466f 100644
> --- a/examples/vhost/main.c
> +++ b/examples/vhost/main.c
> @@ -1048,9 +1048,9 @@ static unsigned check_ports_num(unsigned nb_ports)
>   	}
>   
>   	if (enable_stats) {
> -		__atomic_add_fetch(&dst_vdev->stats.rx_total_atomic, 1,
> +		__atomic_fetch_add(&dst_vdev->stats.rx_total_atomic, 1,
>   				__ATOMIC_SEQ_CST);
> -		__atomic_add_fetch(&dst_vdev->stats.rx_atomic, ret,
> +		__atomic_fetch_add(&dst_vdev->stats.rx_atomic, ret,
>   				__ATOMIC_SEQ_CST);
>   		src_vdev->stats.tx_total++;
>   		src_vdev->stats.tx += ret;
> @@ -1068,9 +1068,9 @@ static unsigned check_ports_num(unsigned nb_ports)
>   	ret = vdev_queue_ops[vdev->vid].enqueue_pkt_burst(vdev, VIRTIO_RXQ, m, nr_xmit);
>   
>   	if (enable_stats) {
> -		__atomic_add_fetch(&vdev->stats.rx_total_atomic, nr_xmit,
> +		__atomic_fetch_add(&vdev->stats.rx_total_atomic, nr_xmit,
>   				__ATOMIC_SEQ_CST);
> -		__atomic_add_fetch(&vdev->stats.rx_atomic, ret,
> +		__atomic_fetch_add(&vdev->stats.rx_atomic, ret,
>   				__ATOMIC_SEQ_CST);
>   	}
>   
> @@ -1400,9 +1400,9 @@ static void virtio_tx_offload(struct rte_mbuf *m)
>   	}
>   
>   	if (enable_stats) {
> -		__atomic_add_fetch(&vdev->stats.rx_total_atomic, rx_count,
> +		__atomic_fetch_add(&vdev->stats.rx_total_atomic, rx_count,
>   				__ATOMIC_SEQ_CST);
> -		__atomic_add_fetch(&vdev->stats.rx_atomic, enqueue_count,
> +		__atomic_fetch_add(&vdev->stats.rx_atomic, enqueue_count,
>   				__ATOMIC_SEQ_CST);
>   	}
>   
> diff --git a/examples/vhost/virtio_net.c b/examples/vhost/virtio_net.c
> index 1d4737f..514c8e0 100644
> --- a/examples/vhost/virtio_net.c
> +++ b/examples/vhost/virtio_net.c
> @@ -231,7 +231,7 @@
>   			rte_prefetch0(&vr->desc[desc_indexes[i+1]]);
>   	}
>   
> -	__atomic_add_fetch(&vr->used->idx, count, __ATOMIC_RELEASE);
> +	__atomic_fetch_add(&vr->used->idx, count, __ATOMIC_RELEASE);
>   	queue->last_used_idx += count;
>   
>   	rte_vhost_vring_call(dev->vid, queue_id);
> @@ -442,7 +442,7 @@
>   	queue->last_avail_idx += i;
>   	queue->last_used_idx += i;
>   
> -	__atomic_add_fetch(&vr->used->idx, i, __ATOMIC_ACQ_REL);
> +	__atomic_fetch_add(&vr->used->idx, i, __ATOMIC_ACQ_REL);
>   
>   	rte_vhost_vring_call(dev->vid, queue_id);
>   

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

Thanks,
Maxime