[Python-checkins] r42782 - python/branches/tim-obmalloc/Objects/obmalloc.c

[tim.peters]

Author: tim.peters
Date: Thu Mar  2 17:58:17 2006
New Revision: 42782

Modified:
   python/branches/tim-obmalloc/Objects/obmalloc.c
Log:
Renamed available_arenas to unused_arena_objects, and
documented its key invariant (an arena_object is on
this list iff its .address member is 0).


Modified: python/branches/tim-obmalloc/Objects/obmalloc.c
==============================================================================
--- python/branches/tim-obmalloc/Objects/obmalloc.c	(original)
+++ python/branches/tim-obmalloc/Objects/obmalloc.c	Thu Mar  2 17:58:17 2006
@@ -271,7 +271,7 @@
 
 	/* Whenever this arena_object is not associated with an allocated
 	 * arena, the nextarena member is used to link all unassociated
-	 * arena_objects in the singly-linked `available_arenas` list.
+	 * arena_objects in the singly-linked `unused_arena_objects` list.
 	 * The prevarena member is unused in this case.
 	 *
 	 * When this arena_object is associated with an allocated arena
@@ -446,12 +446,13 @@
 we do try to free() arenas, and use some mild heuristic strategies to increase
 the likelihood that arenas eventually can be freed.
 
-available_arenas
+unused_arena_objects
 
     This is a singly-linked list of the arena_objects that are currently not
     being used (no arena is associated with them).  Objects are taken off the
     head of the list in new_arena(), and are pushed on the head of the list in
-    PyObject_Free() when the arena is empty.
+    PyObject_Free() when the arena is empty.  Key invariant:  an arena_object
+    is on this list if and only if its .address member is 0.
 
 usable_arenas
 
@@ -463,6 +464,9 @@
     used arena, which gives the nearly empty arenas a chance to be returned to
     the system.  In my unscientific tests this dramatically improved the
     number of arenas that could be freed.
+
+Note that an arena_object associated with an arena all of whose pools are
+currently in use isn't on either list.
 */
 
 /* Array of objects used to track chunks of memory (arenas). */
@@ -473,7 +477,7 @@
 /* The head of the singly-linked, NULL-terminated list of available
  * arena_objects.
  */
-static struct arena_object* available_arenas = NULL;
+static struct arena_object* unused_arena_objects = NULL;
 
 /* The head of the doubly-linked, NULL-terminated at each end, list of
  * arena_objects associated with arenas that have pools available.
@@ -511,7 +515,7 @@
 	if (Py_GETENV("PYTHONMALLOCSTATS"))
 		_PyObject_DebugMallocStats();
 #endif
-	if (available_arenas == NULL) {
+	if (unused_arena_objects == NULL) {
 		uint i;
 		uint numarenas;
 		size_t nbytes;
@@ -537,9 +541,9 @@
 		 * invalid pointers.  Just to be sure, some asserts:
 		 */
 		assert(usable_arenas == NULL);
-		assert(available_arenas == NULL);
+		assert(unused_arena_objects == NULL);
 
-		/* Put the new arenas on the available_arenas list. */
+		/* Put the new arenas on the unused_arena_objects list. */
 		for (i = maxarenas; i < numarenas; ++i) {
 			arenas[i].address = 0;	/* mark as unassociated */
 			arenas[i].nextarena = i < numarenas - 1 ?
@@ -547,22 +551,22 @@
 		}
 
 		/* Update globals. */
-		available_arenas = &arenas[maxarenas];
+		unused_arena_objects = &arenas[maxarenas];
 		maxarenas = numarenas;
 	}
 
 	/* Take the next available arena object off the head of the list. */
-	assert(available_arenas != NULL);
-	arenaobj = available_arenas;
-	available_arenas = arenaobj->nextarena;
+	assert(unused_arena_objects != NULL);
+	arenaobj = unused_arena_objects;
+	unused_arena_objects = arenaobj->nextarena;
 	assert(arenaobj->address == 0);
 	arenaobj->address = (uptr)malloc(ARENA_SIZE);
 	if (arenaobj->address == 0) {
 		/* The allocation failed: return NULL after putting the
 		 * arenaobj back.
 		 */
-		arenaobj->nextarena = available_arenas;
-		available_arenas = arenaobj;
+		arenaobj->nextarena = unused_arena_objects;
+		unused_arena_objects = arenaobj;
 		return NULL;
 	}
 
@@ -986,8 +990,8 @@
 				/* Record that this arena_object slot is
 				 * available to be reused.
 				 */
-				ao->nextarena = available_arenas;
-				available_arenas = ao;
+				ao->nextarena = unused_arena_objects;
+				unused_arena_objects = ao;
 
 				/* Free the entire arena. */
 				free((void *)ao->address);