Re: [PATCH v13 9/9] lib/nodemask: Optimize node_random for nodemask with single NUMA node

[Huang, Ying]

"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> writes:

> The most common case for certain node_random usage (demotion nodemask) is with
> nodemask weight 1. We can avoid calling get_random_init() in that case and
> always return the only node set in the nodemask.

I think that this patch can sit between [5/9] and [6/9], just after it
is used.

> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> ---
>  lib/nodemask.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/lib/nodemask.c b/lib/nodemask.c
> index e22647f5181b..c91a6b0404a5 100644
> --- a/lib/nodemask.c
> +++ b/lib/nodemask.c
> @@ -20,12 +20,21 @@ EXPORT_SYMBOL(__next_node_in);
>   */
>  int node_random(const nodemask_t *maskp)
>  {
> -	int w, bit = NUMA_NO_NODE;
> +	int w, bit;
>  
>  	w = nodes_weight(*maskp);
> -	if (w)
> +	switch (w) {
> +	case 0:
> +		bit = NUMA_NO_NODE;
> +		break;
> +	case 1:
> +		bit = __first_node(maskp);

Per my understanding, first_node() is the formal API and we should use
that?  Just like we use nodes_weight() instead of __nodes_weight().

Best Regards,
Huang, Ying

> +		break;
> +	default:
>  		bit = bitmap_ord_to_pos(maskp->bits,
> -			get_random_int() % w, MAX_NUMNODES);
> +					get_random_int() % w, MAX_NUMNODES);
> +		break;
> +	}
>  	return bit;
>  }
>  #endif