Make the garbage collector aware of malloced bytes, to

prevent skyrocketing memory use when the program manipulates
heap objects that have large amounts of malloc memory
attached, like very large bignums.

* gc.c (MALLOC_DELTA_THRESH): New preprocessor symbol.
(prev_malloc_bytes): New static variable.
(make_obj): when the value of malloc_bytes jumps by MALLOC_DELTA_THRESH
or more since the last gc, trigger gc.

2 files changed, 22 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index eb578f74..f23f8107 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2014-09-06  Kaz Kylheku  <kaz@kylheku.com>
+
+	Make the garbage collector aware of malloced bytes, to
+	prevent skyrocketing memory use when the program manipulates
+	heap objects that have large amounts of malloc memory
+	attached, like very large bignums.
+
+	* gc.c (MALLOC_DELTA_THRESH): New preprocessor symbol.
+	(prev_malloc_bytes): New static variable.
+	(make_obj): when the value of malloc_bytes jumps by MALLOC_DELTA_THRESH
+	or more since the last gc, trigger gc.
+
 2014-09-03  Kaz Kylheku  <kaz@kylheku.com>
 
 	* lib.c (symbol_setname): New static function.
diff --git a/gc.c b/gc.c
index 9d5b61b9..3143530a 100644
--- a/gc.c
+++ b/gc.c
@@ -49,6 +49,7 @@
 #define MUTOBJ_VEC_SIZE         (HEAP_SIZE / 4)
 #define FULL_GC_INTERVAL        40
 #define FRESHOBJ_VEC_SIZE       (8 * HEAP_SIZE)
+#define MALLOC_DELTA_THRESH     (64L * 1024 * 1024)
 
 typedef struct heap {
   struct heap *next;
@@ -76,6 +77,7 @@ static heap_t *heap_list;
 static val heap_min_bound, heap_max_bound;
 
 alloc_bytes_t gc_bytes;
+static alloc_bytes_t prev_malloc_bytes;
 
 int gc_enabled = 1;
 
@@ -153,17 +155,22 @@ static void more(void)
 val make_obj(void)
 {
   int tries;
-
+  alloc_bytes_t malloc_delta = malloc_bytes - prev_malloc_bytes;
   assert (!async_sig_enabled);
 
 #if CONFIG_GEN_GC
-  if (opt_gc_debug || freshobj_idx >= FRESHOBJ_VEC_SIZE) {
+  if (opt_gc_debug || freshobj_idx >= FRESHOBJ_VEC_SIZE ||
+      malloc_delta >= MALLOC_DELTA_THRESH)
+  {
     gc();
     assert (freshobj_idx < FRESHOBJ_VEC_SIZE);
+    prev_malloc_bytes = malloc_bytes;
   }
 #else
-  if (opt_gc_debug)
+  if (opt_gc_debug || malloc_delta >= MALLOC_DELTA_THRESH) {
     gc();
+    prev_malloc_bytes = malloc_bytes;
+  }
 #endif
 
   for (tries = 0; tries < 3; tries++) {