Re: [RFC v1 04/14] bus1: util - fixed list utility library

[Peter Zijlstra]

On Wed, Oct 26, 2016 at 09:18:00PM +0200, David Herrmann wrote:
> +		e = kmalloc_array(sizeof(*e), BUS1_FLIST_BATCH + 1, gfp);

> +#define BUS1_FLIST_BATCH (1024)

> +struct bus1_flist {
> +	union {
> +		struct bus1_flist *next;
> +		void *ptr;
> +	};
> +};

So that's an allocation of 8*(1024+1), or slightly more than 2 pages.

kmalloc will round up to the next power of two, so you'll end up with an
allocation of 16*1024, wasting a whopping 8184 bytes per such allocation
in slack space.

Please consider using 1023 or something for your batch size, 511 would
get you to exactly 1 page which would be even better.