diff --git a/include/jemalloc/internal/bin.h b/include/jemalloc/internal/bin.h
index 4e551663..89572fa1 100644
--- a/include/jemalloc/internal/bin.h
+++ b/include/jemalloc/internal/bin.h
@@ -78,10 +78,29 @@ struct bin_s {
 	malloc_bin_stats_t	stats;
 };
 
-/* Returns true on error. */
+/* Initializes a bin to empty.  Returns true on error. */
 bool bin_init(bin_t *bin);
+
+/* Forking. */
 void bin_prefork(tsdn_t *tsdn, bin_t *bin);
 void bin_postfork_parent(tsdn_t *tsdn, bin_t *bin);
 void bin_postfork_child(tsdn_t *tsdn, bin_t *bin);
 
+/* Stats. */
+static inline void
+bin_stats_merge(tsdn_t *tsdn, malloc_bin_stats_t *dst_bin_stats, bin_t *bin) {
+	malloc_mutex_lock(tsdn, &bin->lock);
+	malloc_mutex_prof_read(tsdn, &dst_bin_stats->mutex_data, &bin->lock);
+	dst_bin_stats->nmalloc += bin->stats.nmalloc;
+	dst_bin_stats->ndalloc += bin->stats.ndalloc;
+	dst_bin_stats->nrequests += bin->stats.nrequests;
+	dst_bin_stats->curregs += bin->stats.curregs;
+	dst_bin_stats->nfills += bin->stats.nfills;
+	dst_bin_stats->nflushes += bin->stats.nflushes;
+	dst_bin_stats->nslabs += bin->stats.nslabs;
+	dst_bin_stats->reslabs += bin->stats.reslabs;
+	dst_bin_stats->curslabs += bin->stats.curslabs;
+	malloc_mutex_unlock(tsdn, &bin->lock);
+}
+
 #endif /* JEMALLOC_INTERNAL_BIN_H */
diff --git a/include/jemalloc/internal/stats.h b/include/jemalloc/internal/stats.h
index f19df374..1da5b024 100644
--- a/include/jemalloc/internal/stats.h
+++ b/include/jemalloc/internal/stats.h
@@ -6,6 +6,12 @@
 #include "jemalloc/internal/mutex.h"
 #include "jemalloc/internal/size_classes.h"
 
+/*
+ * The synchronization for stats counters may piggyback on existing
+ * synchronization in the associated data.  Therefore, the merging functions for
+ * a module's stats will lie in the module, instead of with the stats.
+ */
+
 /*  OPTION(opt,		var_name,	default,	set_value_to) */
 #define STATS_PRINT_OPTIONS						\
     OPTION('J',		json,		false,		true)		\
diff --git a/src/arena.c b/src/arena.c
index a5f24498..c02dff18 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -337,20 +337,7 @@ arena_stats_merge(tsdn_t *tsdn, arena_t *arena, unsigned *nthreads,
 	nstime_subtract(&astats->uptime, &arena->create_time);
 
 	for (szind_t i = 0; i < NBINS; i++) {
-		bin_t *bin = &arena->bins[i];
-
-		malloc_mutex_lock(tsdn, &bin->lock);
-		malloc_mutex_prof_read(tsdn, &bstats[i].mutex_data, &bin->lock);
-		bstats[i].nmalloc += bin->stats.nmalloc;
-		bstats[i].ndalloc += bin->stats.ndalloc;
-		bstats[i].nrequests += bin->stats.nrequests;
-		bstats[i].curregs += bin->stats.curregs;
-		bstats[i].nfills += bin->stats.nfills;
-		bstats[i].nflushes += bin->stats.nflushes;
-		bstats[i].nslabs += bin->stats.nslabs;
-		bstats[i].reslabs += bin->stats.reslabs;
-		bstats[i].curslabs += bin->stats.curslabs;
-		malloc_mutex_unlock(tsdn, &bin->lock);
+		bin_stats_merge(tsdn, &bstats[i], &arena->bins[i]);
 	}
 }