Index: gc.c
===================================================================
--- gc.c	(revision 26813)
+++ gc.c	(working copy)
@@ -284,7 +284,10 @@
 
 #define HEAP_MIN_SLOTS 10000
 #define FREE_MIN  4096
+#define HEAP_GROW_FACTOR 1.8
 
+static float HEAP_GROW_FACTOR_VAL = HEAP_GROW_FACTOR;
+
 struct gc_list {
     VALUE *varptr;
     struct gc_list *next;
@@ -977,7 +980,7 @@
 static void
 set_heaps_increment(rb_objspace_t *objspace)
 {
-    size_t next_heaps_length = (size_t)(heaps_used * 1.8);
+    size_t next_heaps_length = (size_t)(heaps_used * HEAP_GROW_FACTOR_VAL);
 
     if (next_heaps_length == heaps_used) {
         next_heaps_length++;
@@ -2981,6 +2984,38 @@
     return UINT2NUM((&rb_objspace)->count);
 }
 
+/*
+ *  call-seq:
+ *     GC.heap_growth_factor -> Float
+ *
+ *  The rate by which we increase the size of each subsequently allocated heap.
+ *
+ *  It returns the rate by which we increase the size of each subsequently allocated heap.
+ */
+ 
+static VALUE
+gc_heap_growth_factor_get(VALUE self)
+{
+    return rb_float_new(HEAP_GROW_FACTOR_VAL);
+}
+
+/*
+ *
+ *  call-seq:
+ *     GC.heap_growth_factor = Float   -> Float
+ *
+ *  Updates the minimum number of slots in each heap slab.
+ *
+ *  It returns the new number of slots to allocate for each heap slab.
+ */
+ 
+static VALUE
+gc_heap_growth_factor_set(VALUE self, VALUE new_factor)
+{
+    HEAP_GROW_FACTOR_VAL = RFLOAT_VALUE(new_factor);
+    return new_factor;
+}
+
 #if CALC_EXACT_MALLOC_SIZE
 /*
  *  call-seq:
@@ -3147,6 +3182,8 @@
     rb_define_singleton_method(rb_mGC, "stress", gc_stress_get, 0);
     rb_define_singleton_method(rb_mGC, "stress=", gc_stress_set, 1);
     rb_define_singleton_method(rb_mGC, "count", gc_count, 0);
+    rb_define_singleton_method(rb_mGC, "heap_growth_factor", gc_heap_growth_factor_get, 0);
+    rb_define_singleton_method(rb_mGC, "heap_growth_factor=", gc_heap_growth_factor_set, 1);
     rb_define_method(rb_mGC, "garbage_collect", rb_gc_start, 0);
 
     rb_mProfiler = rb_define_module_under(rb_mGC, "Profiler");