MINOR: pool: only use opportunistic versions of the swrate_add() functions

We don't need to know very accurately how much RAM is needed in a pool,
however we must not spend time competing with other threads trying to be
the one with the most accurate value. Let's use the "_opportunistic"
variants of swrate_add() which will simply cause some updates to be
dropped in case of thread contention. This should significantly improve
the situation when dealing with many threads and small per-thread caches.

Performance gains of up to 1-2% were observed on 48-thread systems thanks
to this alone.

diff --git a/src/pool.c b/src/pool.c
index df9d06090700a5ab26fec1cd517f84c5fb4262cc..610e20cc365bdbfae541a5e873b25d4d33efb5b5 100644 (file)
--- a/src/pool.c
+++ b/src/pool.c
@@ -380,7 +380,7 @@ void *pool_alloc_nocache(struct pool_head *pool)
        if (!ptr)
                return NULL;
 
-       swrate_add_scaled(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used, POOL_AVG_SAMPLES/4);
+       swrate_add_scaled_opportunistic(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used, POOL_AVG_SAMPLES/4);
        _HA_ATOMIC_INC(&pool->used);
 
        /* keep track of where the element was allocated from */
@@ -396,7 +396,7 @@ void *pool_alloc_nocache(struct pool_head *pool)
 void pool_free_nocache(struct pool_head *pool, void *ptr)
 {
        _HA_ATOMIC_DEC(&pool->used);
-       swrate_add(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used);
+       swrate_add_opportunistic(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used);
        pool_put_to_os(pool, ptr);
 }
 
@@ -655,7 +655,7 @@ void pool_put_to_shared_cache(struct pool_head *pool, struct pool_item *item, ui
                __ha_barrier_atomic_store();
        } while (!_HA_ATOMIC_CAS(&pool->free_list, &free_list, item));
        __ha_barrier_atomic_store();
-       swrate_add(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used);
+       swrate_add_opportunistic(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used);
 }
 
 /*