Implement metadata statistics.

There are three categories of metadata:

- Base allocations are used for bootstrap-sensitive internal allocator
  data structures.
- Arena chunk headers comprise pages which track the states of the
  non-metadata pages.
- Internal allocations differ from application-originated allocations
  in that they are for internal use, and that they are omitted from heap
  profiles.

The metadata statistics comprise the metadata categories as follows:

- stats.metadata: All metadata -- base + arena chunk headers + internal
  allocations.
- stats.arenas.<i>.metadata.mapped: Arena chunk headers.
- stats.arenas.<i>.metadata.allocated: Internal allocations.  This is
  reported separately from the other metadata statistics because it
  overlaps with the allocated and active statistics, whereas the other
  metadata statistics do not.

Base allocations are not reported separately, though their magnitude can
be computed by subtracting the arena-specific metadata.

This resolves #163.

1 files changed, 1 insertions, 0 deletions

diff --git a/include/jemalloc/internal/ctl.h b/include/jemalloc/internal/ctl.h
index a3e899e..65617bc 100644
--- a/include/jemalloc/internal/ctl.h
+++ b/include/jemalloc/internal/ctl.h
@@ -52,6 +52,7 @@ struct ctl_arena_stats_s {
 struct ctl_stats_s {
 	size_t			allocated;
 	size_t			active;
+	size_t			metadata;
 	size_t			mapped;
 	struct {
 		size_t		current;	/* stats_chunks.curchunks */