[PATCH v1 3/3] gpu/cuda: mem alloc aligned memory

[Stephen Hemminger]

On Tue, 4 Jan 2022 01:47:21 +0000
<eagostini at nvidia.com> wrote:

>  static int
> -cuda_mem_alloc(struct rte_gpu *dev, size_t size, void **ptr)
> +cuda_mem_alloc(struct rte_gpu *dev, size_t size, void **ptr, unsigned int align)
>  {
>  	CUresult res;
>  	const char *err_string;
> @@ -610,8 +612,10 @@ cuda_mem_alloc(struct rte_gpu *dev, size_t size, void **ptr)
>  
>  	/* Allocate memory */
>  	mem_alloc_list_tail->size = size;
> -	res = pfn_cuMemAlloc(&(mem_alloc_list_tail->ptr_d),
> -			mem_alloc_list_tail->size);
> +	mem_alloc_list_tail->size_orig = size + align;
> +
> +	res = pfn_cuMemAlloc(&(mem_alloc_list_tail->ptr_orig_d),
> +			mem_alloc_list_tail->size_orig);
>  	if (res != 0) {
>  		pfn_cuGetErrorString(res, &(err_string));
>  		rte_cuda_log(ERR, "cuCtxSetCurrent current failed with %s",
> @@ -620,6 +624,13 @@ cuda_mem_alloc(struct rte_gpu *dev, size_t size, void **ptr)
>  		return -rte_errno;
>  	}
>  
> +
> +	/* Align memory address */
> +	mem_alloc_list_tail->ptr_d = mem_alloc_list_tail->ptr_orig_d;
> +	if (align && ((uintptr_t)mem_alloc_list_tail->ptr_d) % align)
> +		mem_alloc_list_tail->ptr_d += (align -
> +				(((uintptr_t)mem_alloc_list_tail->ptr_d) % align));


Posix memalign takes size_t for both size and alignment.

Better to put the input parameters first, and then the resulting output parameter last
for consistency; follows the Rusty API design manifesto.

Alignment only makes sense if power of two. The code should check that and optimize
for that.