Re: [dpdk-dev] [PATCH v2] mempool/ring: add support for new ring sync modes

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

Hi Konstantin,

On Mon, Jun 29, 2020 at 05:10:24PM +0100, Konstantin Ananyev wrote:
> v2:
>  - update Release Notes (as per comments)
> 
> Two new sync modes were introduced into rte_ring:
> relaxed tail sync (RTS) and head/tail sync (HTS).
> This change provides user with ability to select these
> modes for ring based mempool via mempool ops API.
> 
> Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> Acked-by: Gage Eads <gage.eads@intel.com>
> ---
>  doc/guides/rel_notes/release_20_08.rst  |  6 ++
>  drivers/mempool/ring/rte_mempool_ring.c | 97 ++++++++++++++++++++++---
>  2 files changed, 94 insertions(+), 9 deletions(-)
> 
> diff --git a/doc/guides/rel_notes/release_20_08.rst b/doc/guides/rel_notes/release_20_08.rst
> index eaaf11c37..7bdcf3aac 100644
> --- a/doc/guides/rel_notes/release_20_08.rst
> +++ b/doc/guides/rel_notes/release_20_08.rst
> @@ -84,6 +84,12 @@ New Features
>    * Dump ``rte_flow`` memory consumption.
>    * Measure packet per second forwarding.
>  
> +* **Added support for new sync modes into mempool ring driver.**
> +
> +  Added ability to select new ring synchronisation modes:
> +  ``relaxed tail sync (ring_mt_rts)`` and ``head/tail sync (ring_mt_hts)``
> +  via mempool ops API.
> +
>  
>  Removed Items
>  -------------
> diff --git a/drivers/mempool/ring/rte_mempool_ring.c b/drivers/mempool/ring/rte_mempool_ring.c
> index bc123fc52..15ec7dee7 100644
> --- a/drivers/mempool/ring/rte_mempool_ring.c
> +++ b/drivers/mempool/ring/rte_mempool_ring.c
> @@ -25,6 +25,22 @@ common_ring_sp_enqueue(struct rte_mempool *mp, void * const *obj_table,
>  			obj_table, n, NULL) == 0 ? -ENOBUFS : 0;
>  }
>  
> +static int
> +rts_ring_mp_enqueue(struct rte_mempool *mp, void * const *obj_table,
> +	unsigned int n)
> +{
> +	return rte_ring_mp_rts_enqueue_bulk(mp->pool_data,
> +			obj_table, n, NULL) == 0 ? -ENOBUFS : 0;
> +}
> +
> +static int
> +hts_ring_mp_enqueue(struct rte_mempool *mp, void * const *obj_table,
> +	unsigned int n)
> +{
> +	return rte_ring_mp_hts_enqueue_bulk(mp->pool_data,
> +			obj_table, n, NULL) == 0 ? -ENOBUFS : 0;
> +}
> +
>  static int
>  common_ring_mc_dequeue(struct rte_mempool *mp, void **obj_table, unsigned n)
>  {
> @@ -39,17 +55,30 @@ common_ring_sc_dequeue(struct rte_mempool *mp, void **obj_table, unsigned n)
>  			obj_table, n, NULL) == 0 ? -ENOBUFS : 0;
>  }
>  
> +static int
> +rts_ring_mc_dequeue(struct rte_mempool *mp, void **obj_table, unsigned int n)
> +{
> +	return rte_ring_mc_rts_dequeue_bulk(mp->pool_data,
> +			obj_table, n, NULL) == 0 ? -ENOBUFS : 0;
> +}
> +
> +static int
> +hts_ring_mc_dequeue(struct rte_mempool *mp, void **obj_table, unsigned int n)
> +{
> +	return rte_ring_mc_hts_dequeue_bulk(mp->pool_data,
> +			obj_table, n, NULL) == 0 ? -ENOBUFS : 0;
> +}
> +
>  static unsigned
>  common_ring_get_count(const struct rte_mempool *mp)
>  {
>  	return rte_ring_count(mp->pool_data);
>  }
>  
> -
>  static int
> -common_ring_alloc(struct rte_mempool *mp)
> +ring_alloc(struct rte_mempool *mp, uint32_t rg_flags)
>  {
> -	int rg_flags = 0, ret;
> +	int ret;
>  	char rg_name[RTE_RING_NAMESIZE];
>  	struct rte_ring *r;
>  
> @@ -60,12 +89,6 @@ common_ring_alloc(struct rte_mempool *mp)
>  		return -rte_errno;
>  	}
>  
> -	/* ring flags */
> -	if (mp->flags & MEMPOOL_F_SP_PUT)
> -		rg_flags |= RING_F_SP_ENQ;
> -	if (mp->flags & MEMPOOL_F_SC_GET)
> -		rg_flags |= RING_F_SC_DEQ;
> -
>  	/*
>  	 * Allocate the ring that will be used to store objects.
>  	 * Ring functions will return appropriate errors if we are
> @@ -82,6 +105,40 @@ common_ring_alloc(struct rte_mempool *mp)
>  	return 0;
>  }
>  
> +static int
> +common_ring_alloc(struct rte_mempool *mp)
> +{
> +	uint32_t rg_flags;
> +
> +	rg_flags = 0;

Maybe it could go on the same line

> +
> +	/* ring flags */

Not sure we need to keep this comment

> +	if (mp->flags & MEMPOOL_F_SP_PUT)
> +		rg_flags |= RING_F_SP_ENQ;
> +	if (mp->flags & MEMPOOL_F_SC_GET)
> +		rg_flags |= RING_F_SC_DEQ;
> +
> +	return ring_alloc(mp, rg_flags);
> +}
> +
> +static int
> +rts_ring_alloc(struct rte_mempool *mp)
> +{
> +	if ((mp->flags & (MEMPOOL_F_SP_PUT | MEMPOOL_F_SC_GET)) != 0)
> +		return -EINVAL;

Why do we need this? It is a problem to allow sc/sp in this mode (even
if it's not optimal)?

> +
> +	return ring_alloc(mp, RING_F_MP_RTS_ENQ | RING_F_MC_RTS_DEQ);
> +}
> +
> +static int
> +hts_ring_alloc(struct rte_mempool *mp)
> +{
> +	if ((mp->flags & (MEMPOOL_F_SP_PUT | MEMPOOL_F_SC_GET)) != 0)
> +		return -EINVAL;
> +
> +	return ring_alloc(mp, RING_F_MP_HTS_ENQ | RING_F_MC_HTS_DEQ);
> +}
> +
>  static void
>  common_ring_free(struct rte_mempool *mp)
>  {
> @@ -130,7 +187,29 @@ static const struct rte_mempool_ops ops_sp_mc = {
>  	.get_count = common_ring_get_count,
>  };
>  
> +/* ops for mempool with ring in MT_RTS sync mode */
> +static const struct rte_mempool_ops ops_mt_rts = {
> +	.name = "ring_mt_rts",
> +	.alloc = rts_ring_alloc,
> +	.free = common_ring_free,
> +	.enqueue = rts_ring_mp_enqueue,
> +	.dequeue = rts_ring_mc_dequeue,
> +	.get_count = common_ring_get_count,
> +};
> +
> +/* ops for mempool with ring in MT_HTS sync mode */
> +static const struct rte_mempool_ops ops_mt_hts = {
> +	.name = "ring_mt_hts",
> +	.alloc = hts_ring_alloc,
> +	.free = common_ring_free,
> +	.enqueue = hts_ring_mp_enqueue,
> +	.dequeue = hts_ring_mc_dequeue,
> +	.get_count = common_ring_get_count,
> +};
> +
>  MEMPOOL_REGISTER_OPS(ops_mp_mc);
>  MEMPOOL_REGISTER_OPS(ops_sp_sc);
>  MEMPOOL_REGISTER_OPS(ops_mp_sc);
>  MEMPOOL_REGISTER_OPS(ops_sp_mc);
> +MEMPOOL_REGISTER_OPS(ops_mt_rts);
> +MEMPOOL_REGISTER_OPS(ops_mt_hts);

Not really related to your patch, but I think we need a function to
dump the name of available mempool ops. We could even add a description.
The problem we have is that a user does not know on which criteria is
should use a driver or another (except for platform drivers).


Olivier