Re: [PATCH v2] ring: add cache guard after ring elements table

[fengchengwen <fengchengwen@huawei.com>]

Acked-by: Chengwen Feng <fengchengwen@huawei.com>

On 5/6/2026 12:13 AM, Morten Brørup wrote:
> Added cache guard after the table holding the ring elements, to avoid
> false sharing conflicts caused by next-line hardware prefetchers when
> accessing elements at the end of the ring table.
> 
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@huawei.com>
> ---
> v2:
> * Added comment describing reason for padding. (Konstantin)
> ---
>  lib/ring/rte_ring.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/lib/ring/rte_ring.c b/lib/ring/rte_ring.c
> index f10050a1c4..10b52dc679 100644
> --- a/lib/ring/rte_ring.c
> +++ b/lib/ring/rte_ring.c
> @@ -73,8 +73,15 @@ rte_ring_get_memsize_elem(unsigned int esize, unsigned int count)
>  		return -EINVAL;
>  	}
>  
> +	static_assert(sizeof(struct rte_ring) == RTE_CACHE_LINE_ROUNDUP(sizeof(struct rte_ring)),
> +			"Size of struct rte_ring not cache line aligned");
>  	sz = sizeof(struct rte_ring) + (ssize_t)count * esize;
> +	/* Add padding, to guard against false sharing-like effects
> +	 * on systems with a next-N-lines hardware prefetcher, when
> +	 * accessing elements at the end of the ring table.
> +	 */
>  	sz = RTE_ALIGN(sz, RTE_CACHE_LINE_SIZE);
> +	sz += RTE_CACHE_GUARD_LINES * RTE_CACHE_LINE_SIZE;
>  	return sz;
>  }
>