Add a hard limit on tcache max size class.

For locality reasons, tcache bins are integrated in TSD.  Allowing all size
classes to be cached has little benefit, but takes up much thread local storage.
In addition, it complicates the layout which we try hard to optimize.

include/jemalloc/internal/tcache_structs.h

@@ -54,7 +54,7 @@ struct tcache_slow_s {
 
 struct tcache_s {
 	tcache_slow_t	*tcache_slow;
-	cache_bin_t	bins[SC_NSIZES];
+	cache_bin_t	bins[TCACHE_NBINS_MAX];
 };
 
 /* Linkage for list of available (previously used) explicit tcache IDs. */

include/jemalloc/internal/tcache_types.h

@@ -27,4 +27,9 @@ typedef struct tcaches_s tcaches_t;
 /* Used for explicit tcache only. Means flushed but not destroyed. */
 #define TCACHES_ELM_NEED_REINIT ((tcache_t *)(uintptr_t)1)
 
+#define TCACHE_LG_MAXCLASS_LIMIT 23 /* tcache_maxclass = 8M */
+#define TCACHE_MAXCLASS_LIMIT ((size_t)1 << TCACHE_LG_MAXCLASS_LIMIT)
+#define TCACHE_NBINS_MAX (SC_NBINS + SC_NGROUP *			\
+    (TCACHE_LG_MAXCLASS_LIMIT - SC_LG_LARGE_MINCLASS) + 1)
+
 #endif /* JEMALLOC_INTERNAL_TCACHE_TYPES_H */