Disable munmap() if it causes VM map holes.

Add a configure test to determine whether common mmap()/munmap()
patterns cause VM map holes, and only use munmap() to discard unused
chunks if the problem does not exist.

Unify the chunk caching for mmap and dss.

Fix options processing to limit lg_chunk to be large enough that
redzones will always fit.

include/jemalloc/internal/chunk_dss.h

@@ -11,7 +11,6 @@
 
 void	*chunk_alloc_dss(size_t size, size_t alignment, bool *zero);
 bool	chunk_in_dss(void *chunk);
-bool	chunk_dealloc_dss(void *chunk, size_t size);
 bool	chunk_dss_boot(void);
 void	chunk_dss_prefork(void);
 void	chunk_dss_postfork_parent(void);

include/jemalloc/internal/chunk_mmap.h

@@ -10,7 +10,7 @@
 #ifdef JEMALLOC_H_EXTERNS
 
 void	*chunk_alloc_mmap(size_t size, size_t alignment);
-void	chunk_dealloc_mmap(void *chunk, size_t size);
+bool	chunk_dealloc_mmap(void *chunk, size_t size);
 
 bool	chunk_mmap_boot(void);
 

include/jemalloc/internal/jemalloc_internal.h.in

@@ -102,6 +102,13 @@ static const bool config_prof_libunwind =
     false
 #endif
     ;
+static const bool config_munmap =
+#ifdef JEMALLOC_MUNMAP
+    true
+#else
+    false
+#endif
+    ;
 static const bool config_stats =
 #ifdef JEMALLOC_STATS
     true

include/jemalloc/internal/private_namespace.h

@@ -57,7 +57,6 @@
 #define	chunk_alloc_mmap JEMALLOC_N(chunk_alloc_mmap)
 #define	chunk_boot JEMALLOC_N(chunk_boot)
 #define	chunk_dealloc JEMALLOC_N(chunk_dealloc)
-#define	chunk_dealloc_dss JEMALLOC_N(chunk_dealloc_dss)
 #define	chunk_dealloc_mmap JEMALLOC_N(chunk_dealloc_mmap)
 #define	chunk_dss_boot JEMALLOC_N(chunk_dss_boot)
 #define	chunk_dss_postfork_child JEMALLOC_N(chunk_dss_postfork_child)

include/jemalloc/jemalloc_defs.h.in

@@ -172,6 +172,14 @@
 /* One page is 2^STATIC_PAGE_SHIFT bytes. */
 #undef STATIC_PAGE_SHIFT
 
+/*
+ * If defined, use munmap() to unmap freed chunks, rather than storing them for
+ * later reuse.  This is automatically disabled if configuration determines
+ * that common sequences of mmap()/munmap() calls will cause virtual memory map
+ * holes.
+ */
+#undef JEMALLOC_MUNMAP
+
 /* TLS is used to map arenas and magazine caches to threads. */
 #undef JEMALLOC_TLS
 
@@ -209,6 +217,13 @@
  */
 #undef JEMALLOC_PURGE_MADVISE_DONTNEED
 #undef JEMALLOC_PURGE_MADVISE_FREE
+#ifdef JEMALLOC_PURGE_MADVISE_DONTNEED
+#  define JEMALLOC_MADV_PURGE MADV_DONTNEED
+#elif defined(JEMALLOC_PURGE_MADVISE_FREE)
+#  define JEMALLOC_MADV_PURGE MADV_FREE
+#else
+#  error "No method defined for purging unused dirty pages."
+#endif
 
 /* sizeof(void *) == 2^LG_SIZEOF_PTR. */
 #undef LG_SIZEOF_PTR