> When built with stats enabled (RTE_LIBRTE_MEMPOOL_STATS defined), the
> performance of mempools with caches is improved as follows.
>
> When accessing objects in the mempool, either the put_bulk and put_objs or
> the get_success_bulk and get_success_objs statistics counters are likely
> to be incremented.
>
> By adding an alternative set of these counters to the mempool cache
> structure, accessing the dedicated statistics structure is avoided in the
> likely cases where these counters are incremented.
>
> The trick here is that the cache line holding the mempool cache structure
> is accessed anyway, in order to access the 'len' or 'flushthresh' fields.
> Updating some statistics counters in the same cache line has lower
> performance cost than accessing the statistics counters in the dedicated
> statistics structure, which resides in another cache line.
>
> mempool_perf_autotest with this patch shows the following improvements in
> rate_persec.
>
> The cost of enabling mempool stats (without debug) after this patch:
> -6.8 % and -6.7 %, respectively without and with cache.
>
> v4:
> * Fix checkpatch warnings:
> A couple of typos in the patch description.
> The macro to add to a mempool cache stat variable should not use
> do {} while (0). Personally, I would tend to disagree with this, but
> whatever keeps the CI happy.
> v3:
> * Don't update the description of the RTE_MEMPOOL_STAT_ADD macro.
> This change belongs in the first patch of the series.
> v2:
> * Move the statistics counters into a stats structure.
>
> Signed-off-by: Morten Brørup <m...@smartsharesystems.com>
> ---
> lib/mempool/rte_mempool.c | 9 ++++++
> lib/mempool/rte_mempool.h | 66 ++++++++++++++++++++++++++++++++-------
> 2 files changed, 64 insertions(+), 11 deletions(-)
>
> diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
> index e6208125e0..a18e39af04 100644
> --- a/lib/mempool/rte_mempool.c
> +++ b/lib/mempool/rte_mempool.c
> @@ -1286,6 +1286,15 @@ rte_mempool_dump(FILE *f, struct rte_mempool *mp)
> sum.get_success_blks += mp->stats[lcore_id].get_success_blks;
> sum.get_fail_blks += mp->stats[lcore_id].get_fail_blks;
> }
> + if (mp->cache_size != 0) {
> + /* Add the statistics stored in the mempool caches. */
> + for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
> + sum.put_bulk +=
> mp->local_cache[lcore_id].stats.put_bulk;
> + sum.put_objs +=
> mp->local_cache[lcore_id].stats.put_objs;
> + sum.get_success_bulk +=
> mp->local_cache[lcore_id].stats.get_success_bulk;
> + sum.get_success_objs +=
> mp->local_cache[lcore_id].stats.get_success_objs;
> + }
> + }
> fprintf(f, " stats:\n");
> fprintf(f, " put_bulk=%"PRIu64"\n", sum.put_bulk);
> fprintf(f, " put_objs=%"PRIu64"\n", sum.put_objs);
> diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
> index abfe34c05f..e6eb573739 100644
> --- a/lib/mempool/rte_mempool.h
> +++ b/lib/mempool/rte_mempool.h
> @@ -86,6 +86,19 @@ 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 */
> +#ifdef RTE_LIBRTE_MEMPOOL_STATS
> + uint32_t unused;
> + /*
> + * Alternative location for the most frequently updated mempool
> statistics (per-lcore),
> + * providing faster update access when using a mempool cache.
> + */
> + struct {
> + uint64_t put_bulk; /**< Number of puts. */
> + uint64_t put_objs; /**< Number of objects successfully
> put. */
> + uint64_t get_success_bulk; /**< Successful allocation number.
> */
> + uint64_t get_success_objs; /**< Objects successfully
> allocated. */
> + } stats; /**< Statistics */
> +#endif
> /**
> * Cache objects
> *
> @@ -319,6 +332,22 @@ struct rte_mempool {
> #define RTE_MEMPOOL_STAT_ADD(mp, name, n) do {} while (0)
> #endif
>
> +/**
> + * @internal When stats is enabled, store some statistics.
> + *
> + * @param cache
> + * Pointer to the memory pool cache.
> + * @param name
> + * Name of the statistics field to increment in the memory pool cache.
> + * @param n
> + * Number to add to the statistics.
> + */
> +#ifdef RTE_LIBRTE_MEMPOOL_STATS
> +#define RTE_MEMPOOL_CACHE_STAT_ADD(cache, name, n) (cache)->stats.name += n
As Andrew already pointed, it needs to be: ((cache)->stats.name += (n))
Apart from that, LGTM.
Series-Acked-by: Konstantin Ananyev <konstantin.anan...@huawei.com>
> +#else
> +#define RTE_MEMPOOL_CACHE_STAT_ADD(cache, name, n) do {} while (0)
> +#endif
> +
> /**
> * @internal Calculate the size of the mempool header.
> *
> @@ -1333,13 +1362,17 @@ rte_mempool_do_generic_put(struct rte_mempool *mp,
> void * const *obj_table,
> {
> void **cache_objs;
>
> + /* No cache provided */
> + if (unlikely(cache == NULL))
> + goto driver_enqueue;
> +
> /* increment stat now, adding in mempool always success */
> - RTE_MEMPOOL_STAT_ADD(mp, put_bulk, 1);
> - RTE_MEMPOOL_STAT_ADD(mp, put_objs, n);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, put_bulk, 1);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, put_objs, n);
>
> - /* No cache provided or the request itself is too big for the cache */
> - if (unlikely(cache == NULL || n > cache->flushthresh))
> - goto driver_enqueue;
> + /* The request itself is too big for the cache */
> + if (unlikely(n > cache->flushthresh))
> + goto driver_enqueue_stats_incremented;
>
> /*
> * The cache follows the following algorithm:
> @@ -1364,6 +1397,12 @@ rte_mempool_do_generic_put(struct rte_mempool *mp,
> void * const *obj_table,
>
> driver_enqueue:
>
> + /* increment stat now, adding in mempool always success */
> + RTE_MEMPOOL_STAT_ADD(mp, put_bulk, 1);
> + RTE_MEMPOOL_STAT_ADD(mp, put_objs, n);
> +
> +driver_enqueue_stats_incremented:
> +
> /* push objects to the backend */
> rte_mempool_ops_enqueue_bulk(mp, obj_table, n);
> }
> @@ -1470,8 +1509,8 @@ rte_mempool_do_generic_get(struct rte_mempool *mp, void
> **obj_table,
> if (remaining == 0) {
> /* The entire request is satisfied from the cache. */
>
> - RTE_MEMPOOL_STAT_ADD(mp, get_success_bulk, 1);
> - RTE_MEMPOOL_STAT_ADD(mp, get_success_objs, n);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_bulk, 1);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_objs, n);
>
> return 0;
> }
> @@ -1500,8 +1539,8 @@ rte_mempool_do_generic_get(struct rte_mempool *mp, void
> **obj_table,
>
> cache->len = cache->size;
>
> - RTE_MEMPOOL_STAT_ADD(mp, get_success_bulk, 1);
> - RTE_MEMPOOL_STAT_ADD(mp, get_success_objs, n);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_bulk, 1);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_objs, n);
>
> return 0;
>
> @@ -1523,8 +1562,13 @@ rte_mempool_do_generic_get(struct rte_mempool *mp,
> void **obj_table,
> RTE_MEMPOOL_STAT_ADD(mp, get_fail_bulk, 1);
> RTE_MEMPOOL_STAT_ADD(mp, get_fail_objs, n);
> } else {
> - RTE_MEMPOOL_STAT_ADD(mp, get_success_bulk, 1);
> - RTE_MEMPOOL_STAT_ADD(mp, get_success_objs, n);
> + if (likely(cache != NULL)) {
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_bulk, 1);
> + RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_objs, n);
> + } else {
> + RTE_MEMPOOL_STAT_ADD(mp, get_success_bulk, 1);
> + RTE_MEMPOOL_STAT_ADD(mp, get_success_objs, n);
> + }
> }
>
> return ret;
> --
> 2.17.1
>
