From: Willy Tarreau <w@1wt.eu>
Date: Thu, 30 Dec 2021 16:20:27 +0000 (+0100)
Subject: MINOR: pool: rely on pool_free_nocache() in pool_put_to_shared_cache()
X-Git-Tag: v2.6-dev1~201
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=57c5c6db0cc67e5d1673dee108712f5e9b603409;p=thirdparty%2Fhaproxy.git

MINOR: pool: rely on pool_free_nocache() in pool_put_to_shared_cache()

At the moment pool_put_to_shared_cache() checks if the pool is crowded,
and if so it does the exact same job as pool_free_nocache(), otherwise
it adds the object there.

This patch rearranges the code so that the function is split in two and
either uses one path or the other, and always relies on pool_free_nocache()
in case we don't want to store the object. This way there will be a common
path with the variant not using the shared cache. The patch is better viewed
using git show -b since a whole block got reindented.

It's worth noting that there is a tiny difference now in the local cache
usage measurement, as the decrement of "used" used to be performed before
checking for pool_is_crowded() instead of being done after. This used to
result in always one less object being kept in the cache than what was
configured in minavail. The rearrangement of the code aligns it with
other call places.
---

diff --git a/include/haproxy/pool.h b/include/haproxy/pool.h
index c899f77664..2a6fa9d427 100644
--- a/include/haproxy/pool.h
+++ b/include/haproxy/pool.h
@@ -142,22 +142,22 @@ static inline void pool_put_to_shared_cache(struct pool_head *pool, void *ptr)
 {
 	void **free_list;
 
-	_HA_ATOMIC_DEC(&pool->used);
-
 	if (unlikely(pool_is_crowded(pool))) {
-		pool_put_to_os(pool, ptr);
-	} else {
-		free_list = _HA_ATOMIC_LOAD(&pool->free_list);
-		do {
-			while (unlikely(free_list == POOL_BUSY)) {
-				__ha_cpu_relax();
-				free_list = _HA_ATOMIC_LOAD(&pool->free_list);
-			}
-			_HA_ATOMIC_STORE((void **)ptr, (void *)free_list);
-			__ha_barrier_atomic_store();
-		} while (!_HA_ATOMIC_CAS(&pool->free_list, &free_list, ptr));
-		__ha_barrier_atomic_store();
+		pool_free_nocache(pool, ptr);
+		return;
 	}
+
+	_HA_ATOMIC_DEC(&pool->used);
+	free_list = _HA_ATOMIC_LOAD(&pool->free_list);
+	do {
+		while (unlikely(free_list == POOL_BUSY)) {
+			__ha_cpu_relax();
+			free_list = _HA_ATOMIC_LOAD(&pool->free_list);
+		}
+		_HA_ATOMIC_STORE((void **)ptr, (void *)free_list);
+		__ha_barrier_atomic_store();
+	} while (!_HA_ATOMIC_CAS(&pool->free_list, &free_list, ptr));
+	__ha_barrier_atomic_store();
 	swrate_add(&pool->needed_avg, POOL_AVG_SAMPLES, pool->used);
 }