Re: [PATCH v4 8/9] dmapool: improve accuracy of debug statistics

[Matthew Wilcox <willy@infradead.org>]

On Mon, Nov 12, 2018 at 10:45:58AM -0500, Tony Battersby wrote:
> +++ linux/mm/dmapool.c	2018-08-06 17:52:53.000000000 -0400
> @@ -61,6 +61,7 @@ struct dma_pool {		/* the pool */
>  	struct device *dev;
>  	unsigned int allocation;
>  	unsigned int boundary;
> +	unsigned int blks_per_alloc;
>  	char name[32];
>  	struct list_head pools;
>  };

This one I'm not totally happy with.  You're storing this value when
it could be easily calculated each time through the show_pools() code.
I appreciate this is a topic where reasonable people might have different
opinions about which solution is preferable.

> @@ -182,6 +182,9 @@ struct dma_pool *dma_pool_create(const c
>  	retval->size = size;
>  	retval->boundary = boundary;
>  	retval->allocation = allocation;
> +	retval->blks_per_alloc =
> +		(allocation / boundary) * (boundary / size) +
> +		(allocation % boundary) / size;
>  
>  	INIT_LIST_HEAD(&retval->pools);
>  
>