Re: [dpdk-dev] custom align for mempool elements

[Olivier Matz <olivier.matz@6wind.com>]

Hi Gregory,

On Wed, 26 Apr 2017 07:00:49 +0300, Gregory Etelson <gregory@weka.io> wrote:
> Signed-off-by: Gregory Etelson <gregory@weka.io>
> ---
>  lib/librte_mempool/rte_mempool.c | 27 ++++++++++++++++++++-------
>  lib/librte_mempool/rte_mempool.h |  1 +
>  2 files changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> index f65310f..c780df3 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -382,7 +382,7 @@ rte_mempool_populate_phys(struct rte_mempool *mp, char *vaddr,
>  	if (mp->flags & MEMPOOL_F_NO_CACHE_ALIGN)
>  		off = RTE_PTR_ALIGN_CEIL(vaddr, 8) - vaddr;
>  	else
> -		off = RTE_PTR_ALIGN_CEIL(vaddr, RTE_CACHE_LINE_SIZE) - vaddr;
> +		off = RTE_PTR_ALIGN_CEIL(vaddr, mp->elt_align) - vaddr;
>  
>  	while (off + total_elt_sz <= len && mp->populated_size < mp->size) {
>  		off += mp->header_size;
> @@ -392,6 +392,7 @@ rte_mempool_populate_phys(struct rte_mempool *mp, char *vaddr,
>  		else
>  			mempool_add_elem(mp, (char *)vaddr + off, paddr + off);
>  		off += mp->elt_size + mp->trailer_size;
> +		off = RTE_ALIGN_CEIL(off, mp->elt_align);
>  		i++;
>  	}
>  
> @@ -508,6 +509,20 @@ rte_mempool_populate_virt(struct rte_mempool *mp, char *addr,
>  	return ret;
>  }
>  
> +static uint32_t
> +mempool_default_elt_aligment(void)
> +{
> +	uint32_t align;
> +	if (rte_xen_dom0_supported()) {
> +		   align = RTE_PGSIZE_2M;;
> +	} else if (rte_eal_has_hugepages()) {
> +		   align = RTE_CACHE_LINE_SIZE;
> +	} else {
> +		   align = getpagesize();
> +	}
> +	return align;
> +}
> +
>  /* Default function to populate the mempool: allocate memory in memzones,
>   * and populate them. Return the number of objects added, or a negative
>   * value on error.
> @@ -518,7 +533,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
>  	int mz_flags = RTE_MEMZONE_1GB|RTE_MEMZONE_SIZE_HINT_ONLY;
>  	char mz_name[RTE_MEMZONE_NAMESIZE];
>  	const struct rte_memzone *mz;
> -	size_t size, total_elt_sz, align, pg_sz, pg_shift;
> +	size_t size, total_elt_sz, pg_sz, pg_shift;
>  	phys_addr_t paddr;
>  	unsigned mz_id, n;
>  	int ret;
> @@ -530,15 +545,12 @@ rte_mempool_populate_default(struct rte_mempool *mp)
>  	if (rte_xen_dom0_supported()) {
>  		pg_sz = RTE_PGSIZE_2M;
>  		pg_shift = rte_bsf32(pg_sz);
> -		align = pg_sz;
>  	} else if (rte_eal_has_hugepages()) {
>  		pg_shift = 0; /* not needed, zone is physically contiguous */
>  		pg_sz = 0;
> -		align = RTE_CACHE_LINE_SIZE;
>  	} else {
>  		pg_sz = getpagesize();
>  		pg_shift = rte_bsf32(pg_sz);
> -		align = pg_sz;
>  	}
>  
>  	total_elt_sz = mp->header_size + mp->elt_size + mp->trailer_size;
> @@ -553,11 +565,11 @@ rte_mempool_populate_default(struct rte_mempool *mp)
>  		}
>  
>  		mz = rte_memzone_reserve_aligned(mz_name, size,
> -			mp->socket_id, mz_flags, align);
> +			mp->socket_id, mz_flags, mp->elt_align);
>  		/* not enough memory, retry with the biggest zone we have */
>  		if (mz == NULL)
>  			mz = rte_memzone_reserve_aligned(mz_name, 0,
> -				mp->socket_id, mz_flags, align);
> +				mp->socket_id, mz_flags, mp->elt_align);
>  		if (mz == NULL) {
>  			ret = -rte_errno;
>  			goto fail;
> @@ -827,6 +839,7 @@ rte_mempool_create_empty(const char *name, unsigned n, unsigned elt_size,
>  	/* Size of default caches, zero means disabled. */
>  	mp->cache_size = cache_size;
>  	mp->private_data_size = private_data_size;
> +	mp->elt_align = mempool_default_elt_aligment();
>  	STAILQ_INIT(&mp->elt_list);
>  	STAILQ_INIT(&mp->mem_list);
>  
> diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
> index 48bc8ea..6631973 100644
> --- a/lib/librte_mempool/rte_mempool.h
> +++ b/lib/librte_mempool/rte_mempool.h
> @@ -245,6 +245,7 @@ struct rte_mempool {
>  	 * this mempool.
>  	 */
>  	int32_t ops_index;
> +	uint32_t elt_align;
>  
>  	struct rte_mempool_cache *local_cache; /**< Per-lcore local cache */
>  

It looks the patch will break the ABI (the mempool structure), so it
has to follow the abi deprecation process (= a notice in 17.05 and
the patch for 17.08).

Could you give us some details about why you need such feature, how you
use it (since no API is added)?

Thanks,
Olivier