Refactor !opt.munmap to opt.retain.

include/jemalloc/internal/arena_structs_b.h

@@ -230,7 +230,7 @@ struct arena_s {
 
 	/*
 	 * Next extent size class in a growing series to use when satisfying a
-	 * request via the extent hooks (only if !opt_munmap).  This limits the
+	 * request via the extent hooks (only if opt_retain).  This limits the
 	 * number of disjoint virtual memory ranges so that extent merging can
 	 * be effective even if multiple arenas' extent allocation requests are
 	 * highly interleaved.

include/jemalloc/internal/extent_mmap_externs.h

@@ -1,7 +1,7 @@
 #ifndef JEMALLOC_INTERNAL_EXTENT_MMAP_EXTERNS_H
 #define JEMALLOC_INTERNAL_EXTENT_MMAP_EXTERNS_H
 
-extern bool	opt_munmap;
+extern bool	opt_retain;
 
 void	*extent_alloc_mmap(void *new_addr, size_t size, size_t alignment,
     bool *zero, bool *commit);

include/jemalloc/internal/extent_structs.h

@@ -59,10 +59,9 @@ struct extent_s {
 	 *
 	 * sn: Serial number (potentially non-unique).
 	 *
-	 *     Serial numbers may wrap around if JEMALLOC_MUNMAP is defined, but
-	 *     as long as comparison functions fall back on address comparison
-	 *     for equal serial numbers, stable (if imperfect) ordering is
-	 *     maintained.
+	 *     Serial numbers may wrap around if !opt_retain, but as long as
+	 *     comparison functions fall back on address comparison for equal
+	 *     serial numbers, stable (if imperfect) ordering is maintained.
 	 *
 	 *     Serial numbers may not be unique even in the absence of
 	 *     wrap-around, e.g. when splitting an extent and assigning the same

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -192,12 +192,12 @@
 #undef JEMALLOC_MAPS_COALESCE
 
 /*
- * If defined, use munmap() to unmap freed extents by default, rather than
- * storing them for later reuse.  This is disabled on 64-bit Linux because
+ * If defined, retain memory for later reuse by default rather than using e.g.
+ * munmap() to unmap freed extents.  This is enabled on 64-bit Linux because
  * common sequences of mmap()/munmap() calls will cause virtual memory map
  * holes.
  */
-#undef JEMALLOC_MUNMAP
+#undef JEMALLOC_RETAIN
 
 /* TLS is used to map arenas and magazine caches to threads. */
 #undef JEMALLOC_TLS

include/jemalloc/internal/stats.h

@@ -117,10 +117,9 @@ typedef struct arena_stats_s {
 	atomic_zu_t		mapped; /* Partially derived. */
 
 	/*
-	 * Number of bytes currently retained as a side effect of munmap() being
-	 * disabled/bypassed.  Retained bytes are technically mapped (though
-	 * always decommitted or purged), but they are excluded from the mapped
-	 * statistic (above).
+	 * Number of unused virtual memory bytes currently retained.  Retained
+	 * bytes are technically mapped (though always decommitted or purged),
+	 * but they are excluded from the mapped statistic (above).
 	 */
 	atomic_zu_t		retained; /* Derived. */