GC tunning simple patch ruby 1.9.2 p180

patch-1.9.2-gc.patch

diff --git a/gc.c b/gc.c
--- a/gc.c
+++ b/gc.c
@@ -77,6 +77,41 @@ void *alloca ();
 #ifndef GC_MALLOC_LIMIT
 #define GC_MALLOC_LIMIT 8000000
 #endif
+#define HEAP_MIN_SLOTS 10000
+#define FREE_MIN  4096
+
+static unsigned int initial_malloc_limit   = GC_MALLOC_LIMIT;
+static unsigned int initial_heap_min_slots = HEAP_MIN_SLOTS;
+static unsigned int initial_free_min       = FREE_MIN;
+
+static void set_gc_parameters()
+{
+   char *malloc_limit_ptr, *heap_min_slots_ptr, *free_min_ptr;
+
+   malloc_limit_ptr = getenv("RUBY_GC_MALLOC_LIMIT");
+   if ( malloc_limit_ptr != NULL ) {
+       int malloc_limit_i = atoi(malloc_limit_ptr);
+       if ( malloc_limit_i > 0 ) {
+	   initial_malloc_limit = malloc_limit_i;
+       }
+   }
+
+   heap_min_slots_ptr = getenv("RUBY_HEAP_MIN_SLOTS");
+   if ( heap_min_slots_ptr != NULL ) {
+       int heap_min_slots_i = atoi(heap_min_slots_ptr);
+       if ( heap_min_slots_i > 0 ) {
+	   initial_heap_min_slots = heap_min_slots_i;
+       }
+   }
+
+   free_min_ptr = getenv("RUBY_FREE_MIN");
+   if ( free_min_ptr != NULL ) {
+       int free_min_i = atoi(free_min_ptr);
+       if ( free_min_i > 0 ) {
+	   initial_free_min = free_min_i;
+       }
+   }
+}
 
 #define nomem_error GET_VM()->special_exceptions[ruby_error_nomemory]
 
@@ -283,9 +318,6 @@ struct heaps_slot {
     int finalize_flag;
 };
 
-#define HEAP_MIN_SLOTS 10000
-#define FREE_MIN  4096
-
 struct gc_list {
     VALUE *varptr;
     struct gc_list *next;
@@ -341,7 +373,7 @@ typedef struct rb_objspace {
 static int ruby_initial_gc_stress = 0;
 int *ruby_initial_gc_stress_ptr = &ruby_initial_gc_stress;
 #else
-static rb_objspace_t rb_objspace = {{GC_MALLOC_LIMIT}, {HEAP_MIN_SLOTS}};
+static rb_objspace_t rb_objspace = {{initial_malloc_limit}, {initial_heap_min_slots}};
 int *ruby_initial_gc_stress_ptr = &rb_objspace.gc_stress;
 #endif
 #define malloc_limit		objspace->malloc_params.limit
@@ -375,7 +407,7 @@ rb_objspace_alloc(void)
 {
     rb_objspace_t *objspace = malloc(sizeof(rb_objspace_t));
     memset(objspace, 0, sizeof(*objspace));
-    malloc_limit = GC_MALLOC_LIMIT;
+    malloc_limit = initial_malloc_limit;
     ruby_gc_stress = ruby_initial_gc_stress;
 
     return objspace;
@@ -958,7 +990,7 @@ init_heap(rb_objspace_t *objspace)
 {
     size_t add, i;
 
-    add = HEAP_MIN_SLOTS / HEAP_OBJ_LIMIT;
+    add = initial_heap_min_slots / HEAP_OBJ_LIMIT;
 
     if (!add) {
         add = 1;
@@ -1862,9 +1894,9 @@ gc_sweep(rb_objspace_t *objspace)
     do_heap_free = (size_t)((heaps_used * HEAP_OBJ_LIMIT) * 0.65);
     free_min = (size_t)((heaps_used * HEAP_OBJ_LIMIT)  * 0.2);
 
-    if (free_min < FREE_MIN) {
+    if (free_min < initial_free_min) {
 	do_heap_free = heaps_used * HEAP_OBJ_LIMIT;
-        free_min = FREE_MIN;
+        free_min = initial_free_min;
     }
 
     freelist = 0;
@@ -1926,7 +1958,7 @@ gc_sweep(rb_objspace_t *objspace)
     GC_PROF_SET_MALLOC_INFO;
     if (malloc_increase > malloc_limit) {
 	malloc_limit += (size_t)((malloc_increase - malloc_limit) * (double)live / (live + freed));
-	if (malloc_limit < GC_MALLOC_LIMIT) malloc_limit = GC_MALLOC_LIMIT;
+	if (malloc_limit < initial_malloc_limit) malloc_limit = initial_malloc_limit;
     }
     malloc_increase = 0;
     if (freed < free_min) {
@@ -2298,6 +2330,7 @@ Init_stack(volatile VALUE *addr)
 void
 Init_heap(void)
 {
+    set_gc_parameters();
     init_heap(&rb_objspace);
 }
 

ah, didn't realize your patchset included this functionality. awesome, i'll check it out, thanks.