Re: [dpdk-dev] [RFC] mempool: implement index-based per core cache

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>
> 
> > Current mempool per core cache implementation is based on pointer For
> > most architectures, each pointer consumes 64b Replace it with
> > index-based implementation, where in each buffer is addressed by (pool
> > address + index)
> 
> I don't think it is going to work:
> On 64-bit systems difference between pool address and it's elem address
> could be bigger than 4GB.
Are you talking about a case where the memory pool size is more than 4GB?

> 
> > It will reduce memory requirements
> >
> > L3Fwd performance testing reveals minor improvements in the cache
> > performance and no change in throughput
> >
> > Micro-benchmarking the patch using mempool_perf_test shows significant
> > improvement with majority of the test cases
> >
> > Future plan involves replacing global pool's pointer-based
> > implementation with index-based implementation
> >
> > Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> > ---
> >  drivers/mempool/ring/rte_mempool_ring.c |  2 +-
> >  lib/mempool/rte_mempool.c               |  8 +++
> >  lib/mempool/rte_mempool.h               | 74 ++++++++++++++++++++++---
> >  3 files changed, 74 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/mempool/ring/rte_mempool_ring.c
> > b/drivers/mempool/ring/rte_mempool_ring.c
> > index b1f09ff28f4d..e55913e47f21 100644
> > --- a/drivers/mempool/ring/rte_mempool_ring.c
> > +++ b/drivers/mempool/ring/rte_mempool_ring.c
> > @@ -101,7 +101,7 @@ ring_alloc(struct rte_mempool *mp, uint32_t
> rg_flags)
> >  		return -rte_errno;
> >
> >  	mp->pool_data = r;
> > -
> > +	mp->local_cache_base_addr = &r[1];
> >  	return 0;
> >  }
> >
> > diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
> > index 59a588425bd6..424bdb19c323 100644
> > --- a/lib/mempool/rte_mempool.c
> > +++ b/lib/mempool/rte_mempool.c
> > @@ -480,6 +480,7 @@ rte_mempool_populate_default(struct
> rte_mempool *mp)
> >  	int ret;
> >  	bool need_iova_contig_obj;
> >  	size_t max_alloc_size = SIZE_MAX;
> > +	unsigned lcore_id;
> >
> >  	ret = mempool_ops_alloc_once(mp);
> >  	if (ret != 0)
> > @@ -600,6 +601,13 @@ rte_mempool_populate_default(struct
> rte_mempool *mp)
> >  		}
> >  	}
> >
> > +	/* Init all default caches. */
> > +	if (mp->cache_size != 0) {
> > +		for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++)
> > +			mp->local_cache[lcore_id].local_cache_base_value =
> > +				*(void **)mp->local_cache_base_addr;
> > +	}
> > +
> >  	rte_mempool_trace_populate_default(mp);
> >  	return mp->size;
> >
> > diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
> > index 4235d6f0bf2b..545405c0d3ce 100644
> > --- a/lib/mempool/rte_mempool.h
> > +++ b/lib/mempool/rte_mempool.h
> > @@ -51,6 +51,8 @@
> >  #include <rte_memcpy.h>
> >  #include <rte_common.h>
> >
> > +#include <arm_neon.h>
> > +
> >  #include "rte_mempool_trace_fp.h"
> >
> >  #ifdef __cplusplus
> > @@ -91,11 +93,12 @@ struct rte_mempool_cache {
> >  	uint32_t size;	      /**< Size of the cache */
> >  	uint32_t flushthresh; /**< Threshold before we flush excess elements
> */
> >  	uint32_t len;	      /**< Current cache count */
> > +	void *local_cache_base_value; /**< Base value to calculate indices
> > +*/
> >  	/*
> >  	 * Cache is allocated to this size to allow it to overflow in certain
> >  	 * cases to avoid needless emptying of cache.
> >  	 */
> > -	void *objs[RTE_MEMPOOL_CACHE_MAX_SIZE * 3]; /**< Cache
> objects */
> > +	uint32_t objs[RTE_MEMPOOL_CACHE_MAX_SIZE * 3]; /**< Cache
> objects */
> >  } __rte_cache_aligned;
> >
> >  /**
> > @@ -172,7 +175,6 @@ struct rte_mempool_objtlr {
> >   * A list of memory where objects are stored
> >   */
> >  STAILQ_HEAD(rte_mempool_memhdr_list, rte_mempool_memhdr);
> > -
> >  /**
> >   * Callback used to free a memory chunk
> >   */
> > @@ -244,6 +246,7 @@ struct rte_mempool {
> >  	int32_t ops_index;
> >
> >  	struct rte_mempool_cache *local_cache; /**< Per-lcore local cache */
> > +	void *local_cache_base_addr; /**< Reference to the base value */
> >
> >  	uint32_t populated_size;         /**< Number of populated objects. */
> >  	struct rte_mempool_objhdr_list elt_list; /**< List of objects in
> > pool */ @@ -1269,7 +1272,15 @@ rte_mempool_cache_flush(struct
> rte_mempool_cache *cache,
> >  	if (cache == NULL || cache->len == 0)
> >  		return;
> >  	rte_mempool_trace_cache_flush(cache, mp);
> > -	rte_mempool_ops_enqueue_bulk(mp, cache->objs, cache->len);
> > +
> > +	unsigned int i;
> > +	unsigned int cache_len = cache->len;
> > +	void *obj_table[RTE_MEMPOOL_CACHE_MAX_SIZE * 3];
> > +	void *base_value = cache->local_cache_base_value;
> > +	uint32_t *cache_objs = cache->objs;
> > +	for (i = 0; i < cache_len; i++)
> > +		obj_table[i] = (void *) RTE_PTR_ADD(base_value,
> cache_objs[i]);
> > +	rte_mempool_ops_enqueue_bulk(mp, obj_table, cache->len);
> >  	cache->len = 0;
> >  }
> >
> > @@ -1289,7 +1300,9 @@ static __rte_always_inline void
> > __mempool_generic_put(struct rte_mempool *mp, void * const *obj_table,
> >  		      unsigned int n, struct rte_mempool_cache *cache)  {
> > -	void **cache_objs;
> > +	uint32_t *cache_objs;
> > +	void *base_value;
> > +	uint32_t i;
> >
> >  	/* increment stat now, adding in mempool always success */
> >  	__MEMPOOL_STAT_ADD(mp, put_bulk, 1); @@ -1301,6 +1314,12
> @@
> > __mempool_generic_put(struct rte_mempool *mp, void * const *obj_table,
> >
> >  	cache_objs = &cache->objs[cache->len];
> >
> > +	base_value = cache->local_cache_base_value;
> > +
> > +	uint64x2_t v_obj_table;
> > +	uint64x2_t v_base_value = vdupq_n_u64((uint64_t)base_value);
> > +	uint32x2_t v_cache_objs;
> > +
> >  	/*
> >  	 * The cache follows the following algorithm
> >  	 *   1. Add the objects to the cache
> > @@ -1309,12 +1328,26 @@ __mempool_generic_put(struct rte_mempool
> *mp, void * const *obj_table,
> >  	 */
> >
> >  	/* Add elements back into the cache */
> > -	rte_memcpy(&cache_objs[0], obj_table, sizeof(void *) * n);
> > +
> > +#if defined __ARM_NEON
> > +	for (i = 0; i < (n & ~0x1); i+=2) {
> > +		v_obj_table = vld1q_u64((const uint64_t *)&obj_table[i]);
> > +		v_cache_objs = vqmovn_u64(vsubq_u64(v_obj_table,
> v_base_value));
> > +		vst1_u32(cache_objs + i, v_cache_objs);
> > +	}
> > +	if (n & 0x1) {
> > +		cache_objs[i] = (uint32_t) RTE_PTR_DIFF(obj_table[i],
> base_value);
> > +	}
> > +#else
> > +	for (i = 0; i < n; i++) {
> > +		cache_objs[i] = (uint32_t) RTE_PTR_DIFF(obj_table[i],
> base_value);
> > +	}
> > +#endif
> >
> >  	cache->len += n;
> >
> >  	if (cache->len >= cache->flushthresh) {
> > -		rte_mempool_ops_enqueue_bulk(mp, &cache->objs[cache-
> >size],
> > +		rte_mempool_ops_enqueue_bulk(mp, obj_table + cache->len
> -
> > +cache->size,
> >  				cache->len - cache->size);
> >  		cache->len = cache->size;
> >  	}
> > @@ -1415,23 +1448,26 @@ __mempool_generic_get(struct rte_mempool
> *mp, void **obj_table,
> >  		      unsigned int n, struct rte_mempool_cache *cache)  {
> >  	int ret;
> > +	uint32_t i;
> >  	uint32_t index, len;
> > -	void **cache_objs;
> > +	uint32_t *cache_objs;
> >
> >  	/* No cache provided or cannot be satisfied from cache */
> >  	if (unlikely(cache == NULL || n >= cache->size))
> >  		goto ring_dequeue;
> >
> > +	void *base_value = cache->local_cache_base_value;
> >  	cache_objs = cache->objs;
> >
> >  	/* Can this be satisfied from the cache? */
> >  	if (cache->len < n) {
> >  		/* No. Backfill the cache first, and then fill from it */
> >  		uint32_t req = n + (cache->size - cache->len);
> > +		void *temp_objs[RTE_MEMPOOL_CACHE_MAX_SIZE * 3];
> /**< Cache objects
> > +*/
> >
> >  		/* How many do we require i.e. number to fill the cache + the
> request */
> >  		ret = rte_mempool_ops_dequeue_bulk(mp,
> > -			&cache->objs[cache->len], req);
> > +			temp_objs, req);
> >  		if (unlikely(ret < 0)) {
> >  			/*
> >  			 * In the off chance that we are buffer constrained,
> @@ -1442,12
> > +1478,32 @@ __mempool_generic_get(struct rte_mempool *mp, void
> **obj_table,
> >  			goto ring_dequeue;
> >  		}
> >
> > +		len = cache->len;
> > +		for (i = 0; i < req; ++i, ++len) {
> > +			cache_objs[len] = (uint32_t)
> RTE_PTR_DIFF(temp_objs[i], base_value);
> > +		}
> > +
> >  		cache->len += req;
> >  	}
> >
> > +	uint64x2_t v_obj_table;
> > +	uint64x2_t v_cache_objs;
> > +	uint64x2_t v_base_value = vdupq_n_u64((uint64_t)base_value);
> > +
> >  	/* Now fill in the response ... */
> > +#if defined __ARM_NEON
> > +	for (index = 0, len = cache->len - 1; index < (n & ~0x1); index+=2,
> > +						len-=2, obj_table+=2) {
> > +		v_cache_objs = vmovl_u32(vld1_u32(cache_objs + len - 1));
> > +		v_obj_table = vaddq_u64(v_cache_objs, v_base_value);
> > +		vst1q_u64((uint64_t *)obj_table, v_obj_table);
> > +	}
> > +	if (n & 0x1)
> > +		*obj_table = (void *) RTE_PTR_ADD(base_value,
> cache_objs[len]);
> > +#else
> >  	for (index = 0, len = cache->len - 1; index < n; ++index, len--,
> obj_table++)
> > -		*obj_table = cache_objs[len];
> > +		*obj_table = (void *) RTE_PTR_ADD(base_value,
> cache_objs[len]);
> > +#endif
> >
> >  	cache->len -= n;
> >
> > --
> > 2.17.1