On Thu, Aug 02, 2018 at 04:01:12PM -0400, Tony Battersby wrote:
> This is my attempt to shrink 'dma_free_o' and 'dma_in_use' in 'struct
> page' (originally 'offset' and 'in_use' in 'struct dma_page') to 16-bit
> so that it is unnecessary to use the '_mapcount' field of 'struct
> page'. However, it adds complexity and makes allocating and freeing up
> to 20% slower for little gain, so I am NOT recommending that it be
> merged at this time. I am posting it just for reference in case someone
> finds it useful in the future.
I spy some interesting pieces in here that I'd love you to submit as
patches for merging.
> One of the nice things about this is that dma_pool_free() can do some
> additional sanity checks:
> *) Check that the offset of the passed-in address corresponds to a valid
> block offset.
Can't we do that already? Subtract the base address of the page from
the passed-in vaddr and check it's a multiple of pool->size?
> struct dma_pool { /* the pool */
> #define POOL_FULL_IDX 0
> #define POOL_AVAIL_IDX 1
> #define POOL_N_LISTS 2
> struct list_head page_list[POOL_N_LISTS];
> spinlock_t lock;
> - size_t size;
> struct device *dev;
> - size_t allocation;
> - size_t boundary;
> + unsigned int size;
> + unsigned int allocation;
> + unsigned int boundary_shift;
> + unsigned int blks_per_boundary;
> + unsigned int blks_per_alloc;
s/size_t/unsigned int/ is a good saving on 64-bit systems. We recently
did something similar for slab/slub.
> @@ -141,6 +150,7 @@ static DEVICE_ATTR(pools, 0444, show_pool
> struct dma_pool *dma_pool_create(const char *name, struct device *dev,
> size_t size, size_t align, size_t boundary)
> {
We should change the API here too.
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