Re: [dpdk-dev] [PATCH v2 08/12] mempool: allow config override on element alignment

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Cyril,

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Cyril Chemparathy
> Sent: Monday, June 22, 2015 7:59 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH v2 08/12] mempool: allow config override on element alignment
> 
> On TILE-Gx and TILE-Mx platforms, the buffers fed into the hardware
> buffer manager require a 128-byte alignment.  With this change, we
> allow configuration based override of the element alignment, and
> default to RTE_CACHE_LINE_SIZE if left unspecified.
> 
> Change-Id: I9cd789d92b0bc9c8f44a633de59bb04d45d927a7
> Signed-off-by: Cyril Chemparathy <cchemparathy@ezchip.com>
> ---
>  lib/librte_mempool/rte_mempool.c | 16 +++++++++-------
>  lib/librte_mempool/rte_mempool.h |  6 ++++++
>  2 files changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> index 002d3a8..7656b0f 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -120,10 +120,10 @@ static unsigned optimize_object_size(unsigned obj_size)
>  		nrank = 1;
> 
>  	/* process new object size */
> -	new_obj_size = (obj_size + RTE_CACHE_LINE_MASK) / RTE_CACHE_LINE_SIZE;
> +	new_obj_size = (obj_size + RTE_MEMPOOL_ALIGN_MASK) / RTE_MEMPOOL_ALIGN;
>  	while (get_gcd(new_obj_size, nrank * nchan) != 1)
>  		new_obj_size++;
> -	return new_obj_size * RTE_CACHE_LINE_SIZE;
> +	return new_obj_size * RTE_MEMPOOL_ALIGN;
>  }
> 
>  static void
> @@ -267,7 +267,7 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
>  #endif
>  	if ((flags & MEMPOOL_F_NO_CACHE_ALIGN) == 0)
>  		sz->header_size = RTE_ALIGN_CEIL(sz->header_size,
> -			RTE_CACHE_LINE_SIZE);
> +			RTE_MEMPOOL_ALIGN);
> 
>  	/* trailer contains the cookie in debug mode */
>  	sz->trailer_size = 0;
> @@ -281,9 +281,9 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
>  	if ((flags & MEMPOOL_F_NO_CACHE_ALIGN) == 0) {
>  		sz->total_size = sz->header_size + sz->elt_size +
>  			sz->trailer_size;
> -		sz->trailer_size += ((RTE_CACHE_LINE_SIZE -
> -				  (sz->total_size & RTE_CACHE_LINE_MASK)) &
> -				 RTE_CACHE_LINE_MASK);
> +		sz->trailer_size += ((RTE_MEMPOOL_ALIGN -
> +				  (sz->total_size & RTE_MEMPOOL_ALIGN_MASK)) &
> +				 RTE_MEMPOOL_ALIGN_MASK);
>  	}
> 
>  	/*
> @@ -498,7 +498,7 @@ rte_mempool_xmem_create(const char *name, unsigned n, unsigned elt_size,
>  	 * cache-aligned
>  	 */
>  	private_data_size = (private_data_size +
> -			     RTE_CACHE_LINE_MASK) & (~RTE_CACHE_LINE_MASK);
> +			     RTE_MEMPOOL_ALIGN_MASK) & (~RTE_MEMPOOL_ALIGN_MASK);
> 
>  	if (! rte_eal_has_hugepages()) {
>  		/*
> @@ -525,6 +525,7 @@ rte_mempool_xmem_create(const char *name, unsigned n, unsigned elt_size,
>  	 * enough to hold mempool header and metadata plus mempool objects.
>  	 */
>  	mempool_size = MEMPOOL_HEADER_SIZE(mp, pg_num) + private_data_size;
> +	mempool_size = RTE_ALIGN_CEIL(mempool_size, RTE_MEMPOOL_ALIGN);
>  	if (vaddr == NULL)
>  		mempool_size += (size_t)objsz.total_size * n;
> 
> @@ -580,6 +581,7 @@ rte_mempool_xmem_create(const char *name, unsigned n, unsigned elt_size,
>  	/* calculate address of the first element for continuous mempool. */
>  	obj = (char *)mp + MEMPOOL_HEADER_SIZE(mp, pg_num) +
>  		private_data_size;
> +	obj = RTE_PTR_ALIGN_CEIL(obj, RTE_MEMPOOL_ALIGN);
> 
>  	/* populate address translation fields. */
>  	mp->pg_num = pg_num;
> diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
> index 380d60b..9321b86 100644
> --- a/lib/librte_mempool/rte_mempool.h
> +++ b/lib/librte_mempool/rte_mempool.h
> @@ -142,6 +142,12 @@ struct rte_mempool_objsz {
>  /** Mempool over one chunk of physically continuous memory */
>  #define	MEMPOOL_PG_NUM_DEFAULT	1
> 
> +#ifndef RTE_MEMPOOL_ALIGN
> +#define RTE_MEMPOOL_ALIGN	RTE_CACHE_LINE_SIZE
> +#endif
> +
> +#define RTE_MEMPOOL_ALIGN_MASK	(RTE_MEMPOOL_ALIGN - 1)

I am probably a bit late with my comments, but why not make it a runtime decision then?
I know we can't add a new parameter to mempool_xmem_create() without ABI breakage,
but we can make some global variable for now, that could be setup at init time or something similar. 

> +
>  /**
>   * Mempool object header structure
>   *
> --
> 2.1.2