[PATCH] eal: add cache guard to per-lcore PRNG state

[Mattias Rönnblom]

On 2023-09-04 11:26, Morten Brørup wrote:
> The per-lcore random state is frequently updated by their individual
> lcores, so add a cache guard to prevent CPU cache thrashing.
> 

"to prevent false sharing in case the CPU employs a next-N-lines (or 
similar) hardware prefetcher"

In my world, cache trashing and cache line contention are two different 
things.

Other than that,
Acked-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>

> Depends-on: series-29415 ("clarify purpose of empty cache lines")
> 
> Signed-off-by: Morten Brørup <mb at smartsharesystems.com>
> ---
>   lib/eal/common/rte_random.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/lib/eal/common/rte_random.c b/lib/eal/common/rte_random.c
> index 565f2401ce..3df0c7004a 100644
> --- a/lib/eal/common/rte_random.c
> +++ b/lib/eal/common/rte_random.c
> @@ -18,6 +18,7 @@ struct rte_rand_state {
>   	uint64_t z3;
>   	uint64_t z4;
>   	uint64_t z5;
> +	RTE_CACHE_GUARD;
>   } __rte_cache_aligned;
>   
>   /* One instance each for every lcore id-equipped thread, and one