Generational GC tweaks.

* gc.c (make_obj): If we have room in the freshobj array,
but are out of objects, then call more. Without this,
we don't take proper advantage of this nursing area.
(gc): Set the full_gc flag after doing gc, in preparation
for next time. If we know full GC is coming, we can
adjust some behaviors. Increase the threshold for calling the more()
function to be the same as in the non-generational case:
less than 3/4 of the size of a heap scavenged.
(gc_set): Now does nothing if it is known that
a full gc is coming. Also, in the checkobj array overflow
case when we invoke gc, there is no point in adding obj
to the array, since it must have been promoted to the mature
generation.
(gc_mutated): Don't bother storing the object in the
array if a full GC is coming.

2 files changed, 45 insertions, 19 deletions

diff --git a/ChangeLog b/ChangeLog
index 3bbbceae..1bf6cf19 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,9 +1,29 @@
 2014-03-29  Kaz Kylheku  <kaz@kylheku.com>
 
+	* gc.c (make_obj): If we have room in the freshobj array,
+	but are out of objects, then call more. Without this,
+	we don't take proper advantage of this nursing area.
+	(gc): Set the full_gc flag after doing gc, in preparation
+	for next time. If we know full GC is coming, we can
+	adjust some behaviors. Increase the threshold for calling the more()
+	function to be the same as in the non-generational case:
+	less than 3/4 of the size of a heap scavenged.
+	(gc_set): Now does nothing if it is known that
+	a full gc is coming. Also, in the checkobj array overflow
+	case when we invoke gc, there is no point in adding obj
+	to the array, since it must have been promoted to the mature
+	generation.
+	(gc_mutated): Don't bother storing the object in the
+	array if a full GC is coming.
+
+2014-03-29  Kaz Kylheku  <kaz@kylheku.com>
+
 	* lib.c (string_time): If possible, change the timezone in the
 	struct tm from "GMT" to "UTC", so that the time_string_utc
 	function will use UTC for the %Z format.
 
+	Generational GC tweaks.
+
 2014-03-27  Kaz Kylheku  <kaz@kylheku.com>
 
 	Fix a bug arising from putting generation 1 objects into the
diff --git a/gc.c b/gc.c
index d58f2a59..2c11d678 100644
--- a/gc.c
+++ b/gc.c
@@ -187,6 +187,13 @@ val make_obj(void)
       return ret;
     }
 
+#if CONFIG_GEN_GC
+    if (freshobj_idx < FRESHOBJ_VEC_SIZE) {
+      more();
+      continue;
+    }
+#endif
+
     switch (tries) {
     case 0: gc(); break;
     case 1: more(); break;
@@ -541,17 +548,12 @@ void gc(void)
   val gc_stack_top = nil;
 #if CONFIG_GEN_GC
   int exhausted = (free_list == 0);
+  int full_gc_next_time = 0;
+  static int gc_counter;
 #endif
 
   if (gc_enabled) {
     int swept;
-#if CONFIG_GEN_GC
-    static int gc_counter;
-    if (++gc_counter >= FULL_GC_INTERVAL) {
-      full_gc = 1;
-      gc_counter = 0;
-    }
-#endif
 
     mach_context_t mc;
     save_context(mc);
@@ -564,9 +566,11 @@ void gc(void)
     printf("sweep: freed %d full_gc == %d exhausted == %d\n",
            (int) swept, full_gc, exhausted);
 #endif
-    if (full_gc && swept < 3 * HEAP_SIZE / 4)
-      more();
-    else if (!full_gc && swept < HEAP_SIZE / 4 && exhausted)
+    if (++gc_counter >= FULL_GC_INTERVAL - 1) {
+      full_gc_next_time = 1;
+      gc_counter = 0;
+    }
+    if (exhausted && full_gc && swept < 3 * HEAP_SIZE / 4)
       more();
 #else
     if (swept < 3 * HEAP_SIZE / 4)
@@ -577,7 +581,7 @@ void gc(void)
     checkobj_idx = 0;
     mutobj_idx = 0;
     freshobj_idx = 0;
-    full_gc = 0;
+    full_gc = full_gc_next_time;
 #endif
     gc_enabled = 1;
   }
@@ -621,12 +625,14 @@ int gc_is_reachable(val obj)
 
 val gc_set(val *ptr, val obj)
 {
-  if (checkobj_idx >= CHECKOBJ_VEC_SIZE) {
-    gc();
-    /* obj can't be in gen 0 because there are no baby objects after gc */
-  } else if (in_malloc_range((mem_t *) ptr) && is_ptr(obj) && obj->t.gen == 0) {
-    obj->t.gen = -1;
-    checkobj[checkobj_idx++] = obj;
+  if (!full_gc) {
+    if (checkobj_idx >= CHECKOBJ_VEC_SIZE) {
+      gc();
+      /* obj can't be in gen 0 because there are no baby objects after gc */
+    } else if (in_malloc_range((mem_t *) ptr) && is_ptr(obj) && obj->t.gen == 0) {
+      obj->t.gen = -1;
+      checkobj[checkobj_idx++] = obj;
+    }
   }
   *ptr = obj;
   return obj;
@@ -635,8 +641,8 @@ val gc_set(val *ptr, val obj)
 val gc_mutated(val obj)
 {
   /* We care only about mature generation objects that have not
-     already been noted. */
-  if (obj->t.gen <= 0)
+     already been noted. And if a full gc is coming, don't bother. */
+  if (full_gc || obj->t.gen <= 0)
     return obj;
   obj->t.gen = -1;
   /* Store in mutobj array *before* triggering gc, otherwise