diff --git a/include/jemalloc/internal/arena_inlines_b.h b/include/jemalloc/internal/arena_inlines_b.h
index 7351db98..335c0797 100644
--- a/include/jemalloc/internal/arena_inlines_b.h
+++ b/include/jemalloc/internal/arena_inlines_b.h
@@ -131,9 +131,6 @@ arena_decay_ticks(tsdn_t *tsdn, arena_t *arena, unsigned nticks) {
 
 JEMALLOC_ALWAYS_INLINE void
 arena_decay_tick(tsdn_t *tsdn, arena_t *arena) {
-	malloc_mutex_assert_not_owner(tsdn, &arena->pa_shard.decay_dirty.mtx);
-	malloc_mutex_assert_not_owner(tsdn, &arena->pa_shard.decay_muzzy.mtx);
-
 	arena_decay_ticks(tsdn, arena, 1);
 }
 
diff --git a/include/jemalloc/internal/background_thread_inlines.h b/include/jemalloc/internal/background_thread_inlines.h
index 7bdbe928..71b433cb 100644
--- a/include/jemalloc/internal/background_thread_inlines.h
+++ b/include/jemalloc/internal/background_thread_inlines.h
@@ -55,7 +55,7 @@ arena_background_thread_inactivity_check(tsdn_t *tsdn, arena_t *arena,
 	    arena_background_thread_info_get(arena);
 	if (background_thread_indefinite_sleep(info)) {
 		background_thread_interval_check(tsdn, arena,
-		    &arena->pa_shard.decay_dirty, 0);
+		    &arena->pa_shard.pac.decay_dirty, 0);
 	}
 }
 
diff --git a/include/jemalloc/internal/pa.h b/include/jemalloc/internal/pa.h
index 0b3e5289..ca6482a8 100644
--- a/include/jemalloc/internal/pa.h
+++ b/include/jemalloc/internal/pa.h
@@ -126,22 +126,12 @@ struct pa_shard_s {
 	/* The source of edata_t objects. */
 	edata_cache_t edata_cache;
 
-
 	/* Extent serial number generator state. */
 	atomic_zu_t extent_sn_next;
 
 	malloc_mutex_t *stats_mtx;
 	pa_shard_stats_t *stats;
 
-	/*
-	 * Decay-based purging state, responsible for scheduling extent state
-	 * transitions.
-	 *
-	 * Synchronization: via the internal mutex.
-	 */
-	decay_t decay_dirty; /* dirty --> muzzy */
-	decay_t decay_muzzy; /* muzzy --> retained */
-
 	/* The emap this shard is tied to. */
 	emap_t *emap;
 
@@ -149,25 +139,16 @@ struct pa_shard_s {
 	base_t *base;
 };
 
-static inline ssize_t
-pa_shard_dirty_decay_ms_get(pa_shard_t *shard) {
-	return decay_ms_read(&shard->decay_dirty);
-}
-static inline ssize_t
-pa_shard_muzzy_decay_ms_get(pa_shard_t *shard) {
-	return decay_ms_read(&shard->decay_muzzy);
-}
-
 static inline bool
 pa_shard_dont_decay_muzzy(pa_shard_t *shard) {
 	return ecache_npages_get(&shard->pac.ecache_muzzy) == 0 &&
-	    pa_shard_muzzy_decay_ms_get(shard) <= 0;
+	    pac_muzzy_decay_ms_get(&shard->pac) <= 0;
 }
 
 static inline bool
 pa_shard_may_force_decay(pa_shard_t *shard) {
-	return !(pa_shard_dirty_decay_ms_get(shard) == -1
-	    || pa_shard_muzzy_decay_ms_get(shard) == -1);
+	return !(pac_dirty_decay_ms_get(&shard->pac) == -1
+	    || pac_muzzy_decay_ms_get(&shard->pac) == -1);
 }
 
 static inline ehooks_t *
diff --git a/include/jemalloc/internal/pac.h b/include/jemalloc/internal/pac.h
index 3ad00970..da14b621 100644
--- a/include/jemalloc/internal/pac.h
+++ b/include/jemalloc/internal/pac.h
@@ -26,11 +26,31 @@ struct pac_s {
 
 	/* The grow info for the retained ecache. */
 	ecache_grow_t ecache_grow;
+
+	/*
+	 * Decay-based purging state, responsible for scheduling extent state
+	 * transitions.
+	 *
+	 * Synchronization: via the internal mutex.
+	 */
+	decay_t decay_dirty; /* dirty --> muzzy */
+	decay_t decay_muzzy; /* muzzy --> retained */
 };
 
 bool pac_init(tsdn_t *tsdn, pac_t *pac, unsigned ind, emap_t *emap,
-    edata_cache_t *edata_cache);
+    edata_cache_t *edata_cache, nstime_t *cur_time, ssize_t dirty_decay_ms,
+    ssize_t muzzy_decay_ms);
 bool pac_retain_grow_limit_get_set(tsdn_t *tsdn, pac_t *pac, size_t *old_limit,
     size_t *new_limit);
 
+static inline ssize_t
+pac_dirty_decay_ms_get(pac_t *pac) {
+	return decay_ms_read(&pac->decay_dirty);
+}
+
+static inline ssize_t
+pac_muzzy_decay_ms_get(pac_t *pac) {
+	return decay_ms_read(&pac->decay_muzzy);
+}
+
 #endif /* JEMALLOC_INTERNAL_PAC_H */
diff --git a/src/arena.c b/src/arena.c
index fb9cb7b5..9fa2db7f 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -397,12 +397,12 @@ arena_extent_ralloc_large_expand(tsdn_t *tsdn, arena_t *arena, edata_t *edata,
 
 ssize_t
 arena_dirty_decay_ms_get(arena_t *arena) {
-	return pa_shard_dirty_decay_ms_get(&arena->pa_shard);
+	return pac_dirty_decay_ms_get(&arena->pa_shard.pac);
 }
 
 ssize_t
 arena_muzzy_decay_ms_get(arena_t *arena) {
-	return pa_shard_muzzy_decay_ms_get(&arena->pa_shard);
+	return pac_muzzy_decay_ms_get(&arena->pa_shard.pac);
 }
 
 /*
@@ -453,7 +453,7 @@ arena_decay_ms_set(tsdn_t *tsdn, arena_t *arena, decay_t *decay,
 bool
 arena_dirty_decay_ms_set(tsdn_t *tsdn, arena_t *arena,
     ssize_t decay_ms) {
-	return arena_decay_ms_set(tsdn, arena, &arena->pa_shard.decay_dirty,
+	return arena_decay_ms_set(tsdn, arena, &arena->pa_shard.pac.decay_dirty,
 	    &arena->pa_shard.stats->decay_dirty,
 	    &arena->pa_shard.pac.ecache_dirty, decay_ms);
 }
@@ -461,7 +461,7 @@ arena_dirty_decay_ms_set(tsdn_t *tsdn, arena_t *arena,
 bool
 arena_muzzy_decay_ms_set(tsdn_t *tsdn, arena_t *arena,
     ssize_t decay_ms) {
-	return arena_decay_ms_set(tsdn, arena, &arena->pa_shard.decay_muzzy,
+	return arena_decay_ms_set(tsdn, arena, &arena->pa_shard.pac.decay_muzzy,
 	    &arena->pa_shard.stats->decay_muzzy,
 	    &arena->pa_shard.pac.ecache_muzzy, decay_ms);
 }
@@ -520,7 +520,7 @@ arena_decay_impl(tsdn_t *tsdn, arena_t *arena, decay_t *decay,
 static bool
 arena_decay_dirty(tsdn_t *tsdn, arena_t *arena, bool is_background_thread,
     bool all) {
-	return arena_decay_impl(tsdn, arena, &arena->pa_shard.decay_dirty,
+	return arena_decay_impl(tsdn, arena, &arena->pa_shard.pac.decay_dirty,
 	    &arena->pa_shard.stats->decay_dirty,
 	    &arena->pa_shard.pac.ecache_dirty, is_background_thread, all);
 }
@@ -531,7 +531,7 @@ arena_decay_muzzy(tsdn_t *tsdn, arena_t *arena, bool is_background_thread,
 	if (pa_shard_dont_decay_muzzy(&arena->pa_shard)) {
 		return false;
 	}
-	return arena_decay_impl(tsdn, arena, &arena->pa_shard.decay_muzzy,
+	return arena_decay_impl(tsdn, arena, &arena->pa_shard.pac.decay_muzzy,
 	    &arena->pa_shard.stats->decay_muzzy,
 	    &arena->pa_shard.pac.ecache_muzzy, is_background_thread, all);
 }
diff --git a/src/background_thread.c b/src/background_thread.c
index 557dbc41..a36836cb 100644
--- a/src/background_thread.c
+++ b/src/background_thread.c
@@ -201,12 +201,12 @@ static uint64_t
 arena_decay_compute_purge_interval(tsdn_t *tsdn, arena_t *arena) {
 	uint64_t i1, i2;
 	i1 = arena_decay_compute_purge_interval_impl(tsdn,
-	    &arena->pa_shard.decay_dirty, &arena->pa_shard.pac.ecache_dirty);
+	    &arena->pa_shard.pac.decay_dirty, &arena->pa_shard.pac.ecache_dirty);
 	if (i1 == BACKGROUND_THREAD_MIN_INTERVAL_NS) {
 		return i1;
 	}
 	i2 = arena_decay_compute_purge_interval_impl(tsdn,
-	    &arena->pa_shard.decay_muzzy, &arena->pa_shard.pac.ecache_muzzy);
+	    &arena->pa_shard.pac.decay_muzzy, &arena->pa_shard.pac.ecache_muzzy);
 
 	return i1 < i2 ? i1 : i2;
 }
diff --git a/src/ctl.c b/src/ctl.c
index 0098d931..56dcf823 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -3130,8 +3130,8 @@ stats_mutexes_reset_ctl(tsd_t *tsd, const size_t *mib,
 		MUTEX_PROF_RESET(arena->pa_shard.pac.ecache_dirty.mtx);
 		MUTEX_PROF_RESET(arena->pa_shard.pac.ecache_muzzy.mtx);
 		MUTEX_PROF_RESET(arena->pa_shard.pac.ecache_retained.mtx);
-		MUTEX_PROF_RESET(arena->pa_shard.decay_dirty.mtx);
-		MUTEX_PROF_RESET(arena->pa_shard.decay_muzzy.mtx);
+		MUTEX_PROF_RESET(arena->pa_shard.pac.decay_dirty.mtx);
+		MUTEX_PROF_RESET(arena->pa_shard.pac.decay_muzzy.mtx);
 		MUTEX_PROF_RESET(arena->tcache_ql_mtx);
 		MUTEX_PROF_RESET(arena->base->mtx);
 
diff --git a/src/pa.c b/src/pa.c
index 98deba54..501d57c3 100644
--- a/src/pa.c
+++ b/src/pa.c
@@ -29,14 +29,8 @@ pa_shard_init(tsdn_t *tsdn, pa_shard_t *shard, emap_t *emap, base_t *base,
 	if (edata_cache_init(&shard->edata_cache, base)) {
 		return true;
 	}
-	if (pac_init(tsdn, &shard->pac, ind, emap, &shard->edata_cache)) {
-		return true;
-	}
-
-	if (decay_init(&shard->decay_dirty, cur_time, dirty_decay_ms)) {
-		return true;
-	}
-	if (decay_init(&shard->decay_muzzy, cur_time, muzzy_decay_ms)) {
+	if (pac_init(tsdn, &shard->pac, ind, emap, &shard->edata_cache,
+	    cur_time, dirty_decay_ms, muzzy_decay_ms)) {
 		return true;
 	}
 
@@ -91,7 +85,7 @@ pa_shard_extent_sn_next(pa_shard_t *shard) {
 
 static bool
 pa_shard_may_have_muzzy(pa_shard_t *shard) {
-	return pa_shard_muzzy_decay_ms_get(shard) != 0;
+	return pac_muzzy_decay_ms_get(&shard->pac) != 0;
 }
 
 static edata_t *
diff --git a/src/pa_extra.c b/src/pa_extra.c
index a755781c..ae5855aa 100644
--- a/src/pa_extra.c
+++ b/src/pa_extra.c
@@ -10,8 +10,8 @@
 
 void
 pa_shard_prefork0(tsdn_t *tsdn, pa_shard_t *shard) {
-	malloc_mutex_prefork(tsdn, &shard->decay_dirty.mtx);
-	malloc_mutex_prefork(tsdn, &shard->decay_muzzy.mtx);
+	malloc_mutex_prefork(tsdn, &shard->pac.decay_dirty.mtx);
+	malloc_mutex_prefork(tsdn, &shard->pac.decay_muzzy.mtx);
 }
 
 void
@@ -38,8 +38,8 @@ pa_shard_postfork_parent(tsdn_t *tsdn, pa_shard_t *shard) {
 	ecache_postfork_parent(tsdn, &shard->pac.ecache_muzzy);
 	ecache_postfork_parent(tsdn, &shard->pac.ecache_retained);
 	ecache_grow_postfork_parent(tsdn, &shard->pac.ecache_grow);
-	malloc_mutex_postfork_parent(tsdn, &shard->decay_dirty.mtx);
-	malloc_mutex_postfork_parent(tsdn, &shard->decay_muzzy.mtx);
+	malloc_mutex_postfork_parent(tsdn, &shard->pac.decay_dirty.mtx);
+	malloc_mutex_postfork_parent(tsdn, &shard->pac.decay_muzzy.mtx);
 }
 
 void
@@ -49,8 +49,8 @@ pa_shard_postfork_child(tsdn_t *tsdn, pa_shard_t *shard) {
 	ecache_postfork_child(tsdn, &shard->pac.ecache_muzzy);
 	ecache_postfork_child(tsdn, &shard->pac.ecache_retained);
 	ecache_grow_postfork_child(tsdn, &shard->pac.ecache_grow);
-	malloc_mutex_postfork_child(tsdn, &shard->decay_dirty.mtx);
-	malloc_mutex_postfork_child(tsdn, &shard->decay_muzzy.mtx);
+	malloc_mutex_postfork_child(tsdn, &shard->pac.decay_dirty.mtx);
+	malloc_mutex_postfork_child(tsdn, &shard->pac.decay_muzzy.mtx);
 }
 
 void
@@ -148,7 +148,7 @@ pa_shard_mtx_stats_read(tsdn_t *tsdn, pa_shard_t *shard,
 	pa_shard_mtx_stats_read_single(tsdn, mutex_prof_data,
 	    &shard->pac.ecache_retained.mtx, arena_prof_mutex_extents_retained);
 	pa_shard_mtx_stats_read_single(tsdn, mutex_prof_data,
-	    &shard->decay_dirty.mtx, arena_prof_mutex_decay_dirty);
+	    &shard->pac.decay_dirty.mtx, arena_prof_mutex_decay_dirty);
 	pa_shard_mtx_stats_read_single(tsdn, mutex_prof_data,
-	    &shard->decay_muzzy.mtx, arena_prof_mutex_decay_muzzy);
+	    &shard->pac.decay_muzzy.mtx, arena_prof_mutex_decay_muzzy);
 }
diff --git a/src/pac.c b/src/pac.c
index f30c4bbf..1e20d652 100644
--- a/src/pac.c
+++ b/src/pac.c
@@ -5,7 +5,8 @@
 
 bool
 pac_init(tsdn_t *tsdn, pac_t *pac, unsigned ind, emap_t *emap,
-    edata_cache_t *edata_cache) {
+    edata_cache_t *edata_cache, nstime_t *cur_time, ssize_t dirty_decay_ms,
+    ssize_t muzzy_decay_ms) {
 	/*
 	 * Delay coalescing for dirty extents despite the disruptive effect on
 	 * memory layout for best-fit extent allocation, since cached extents
@@ -37,6 +38,12 @@ pac_init(tsdn_t *tsdn, pac_t *pac, unsigned ind, emap_t *emap,
 	if (ecache_grow_init(tsdn, &pac->ecache_grow)) {
 		return true;
 	}
+	if (decay_init(&pac->decay_dirty, cur_time, dirty_decay_ms)) {
+		return true;
+	}
+	if (decay_init(&pac->decay_muzzy, cur_time, muzzy_decay_ms)) {
+		return true;
+	}
 
 	pac->emap = emap;
 	pac->edata_cache = edata_cache;
diff --git a/test/unit/pa.c b/test/unit/pa.c
index 8846f614..7cd9fa17 100644
--- a/test/unit/pa.c
+++ b/test/unit/pa.c
@@ -86,13 +86,14 @@ do_alloc_free_purge(void *arg) {
 		bool generated_dirty;
 		pa_dalloc(TSDN_NULL, &test_data->shard, edata,
 		    &generated_dirty);
-		malloc_mutex_lock(TSDN_NULL, &test_data->shard.decay_dirty.mtx);
+		malloc_mutex_lock(TSDN_NULL,
+		    &test_data->shard.pac.decay_dirty.mtx);
 		pa_decay_all(TSDN_NULL, &test_data->shard,
-		    &test_data->shard.decay_dirty,
+		    &test_data->shard.pac.decay_dirty,
 		    &test_data->stats.decay_dirty,
 		    &test_data->shard.pac.ecache_dirty, true);
 		malloc_mutex_unlock(TSDN_NULL,
-		    &test_data->shard.decay_dirty.mtx);
+		    &test_data->shard.pac.decay_dirty.mtx);
 	}
 	return NULL;
 }