[dpdk-dev] [PATCH 2/2] ring: empty optimization

[Ananyev, Konstantin]

> 
> Testing if the ring is empty is as simple as comparing the producer and
> consumer pointers.
> 
> In theory, this optimization reduces the number of potential cache misses
> from 3 to 2 by not having to read r->mask in rte_ring_count().
> 
> The modification of this function were also discussed in the RFC here:
> https://mails.dpdk.org/archives/dev/2020-April/165752.html
> 
> Signed-off-by: Morten Brørup <mb at smartsharesystems.com>
> ---
>  lib/librte_ring/rte_ring.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
> index 9078e7c24..f67141482 100644
> --- a/lib/librte_ring/rte_ring.h
> +++ b/lib/librte_ring/rte_ring.h
> @@ -733,7 +733,9 @@ rte_ring_full(const struct rte_ring *r)
>  static inline int
>  rte_ring_empty(const struct rte_ring *r)
>  {
> -	return rte_ring_count(r) == 0;
> +	uint32_t prod_tail = r->prod.tail;
> +	uint32_t cons_tail = r->cons.tail;
> +	return cons_tail == prod_tail;
>  }
> 
>  /**
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>

> 2.17.1