Add stats for metadata_thp.

Report number of THPs used in arena and aggregated stats.

include/jemalloc/internal/base_externs.h

@@ -13,7 +13,7 @@ extent_hooks_t *base_extent_hooks_set(base_t *base,
 void *base_alloc(tsdn_t *tsdn, base_t *base, size_t size, size_t alignment);
 extent_t *base_alloc_extent(tsdn_t *tsdn, base_t *base);
 void base_stats_get(tsdn_t *tsdn, base_t *base, size_t *allocated,
-    size_t *resident, size_t *mapped);
+    size_t *resident, size_t *mapped, size_t *n_thp);
 void base_prefork(tsdn_t *tsdn, base_t *base);
 void base_postfork_parent(tsdn_t *tsdn, base_t *base);
 void base_postfork_child(tsdn_t *tsdn, base_t *base);

include/jemalloc/internal/base_structs.h

@@ -50,6 +50,8 @@ struct base_s {
 	size_t		allocated;
 	size_t		resident;
 	size_t		mapped;
+	/* Number of THP regions touched. */
+	size_t		n_thp;
 };
 
 #endif /* JEMALLOC_INTERNAL_BASE_STRUCTS_H */

include/jemalloc/internal/ctl.h

@@ -48,6 +48,7 @@ typedef struct ctl_stats_s {
 	size_t allocated;
 	size_t active;
 	size_t metadata;
+	size_t metadata_thp;
 	size_t resident;
 	size_t mapped;
 	size_t retained;

include/jemalloc/internal/stats.h

@@ -142,6 +142,7 @@ typedef struct arena_stats_s {
 	atomic_zu_t		base; /* Derived. */
 	atomic_zu_t		internal;
 	atomic_zu_t		resident; /* Derived. */
+	atomic_zu_t		metadata_thp;
 
 	atomic_zu_t		allocated_large; /* Derived. */
 	arena_stats_u64_t	nmalloc_large; /* Derived. */