Bug #8093
closed
[patch] gc: avoid unnecessary heap growth
Description
In r37970, the following change was made:
@@ -2063,7 +2070,7 @@ gc_prepare_free_objects(rb_objspace_t *objspace)
gc_marks(objspace);before_gc_sweep(objspace);
- if (objspace->heap.free_min > (heaps_used * HEAP_OBJ_LIMIT - objspace->heap.live_num)) {
- if (objspace->heap.free_min > (heaps_used * HEAP_OBJ_LIMIT - objspace_live_num(objspace))) {
set_heaps_increment(objspace);
}
Here heap.live_num and objspace_live_num() are not equivalent.
heap.live_num is the number of objects marked during mark phase.
objspace_live_num() is the total number of slots in use, including unmarked slots that haven't been swept yet.
Since this check occurs before sweep begins, objspace_live_num() is always greater than heap.live_num. This causes set_heaps_increment to be called more often.
I propose adding the heap.live_num counter back, but with a better name: heap.marked_num.
diff --git a/gc.c b/gc.c
index bd95073..26bfcf8 100644
--- a/gc.c
+++ b/gc.c
@@ -228,6 +228,7 @@ typedef struct rb_objspace {
struct heaps_free_bitmap *free_bitmap;
RVALUE *range[2];
struct heaps_header *freed;
- size_t marked_num;
size_t free_num;
size_t free_min;
size_t final_num;
@@ -2000,7 +2001,7 @@ after_gc_sweep(rb_objspace_t *objspace)
inc = ATOMIC_SIZE_EXCHANGE(malloc_increase, 0);
if (inc > malloc_limit) {
malloc_limit +=
-
(size_t)((inc - malloc_limit) * (double)objspace_live_num(objspace) / (heaps_used * HEAP_OBJ_LIMIT));
-
if (malloc_limit < initial_malloc_limit) malloc_limit = initial_malloc_limit;(size_t)((inc - malloc_limit) * (double)objspace->heap.marked_num / (heaps_used * HEAP_OBJ_LIMIT));
}
@@ -2073,7 +2074,7 @@ gc_prepare_free_objects(rb_objspace_t *objspace)
gc_marks(objspace);
before_gc_sweep(objspace);
- if (objspace->heap.free_min > (heaps_used * HEAP_OBJ_LIMIT - objspace_live_num(objspace))) {
- if (objspace->heap.free_min > (heaps_used * HEAP_OBJ_LIMIT - objspace->heap.marked_num)) {
set_heaps_increment(objspace);
}
@@ -2561,6 +2562,7 @@ gc_mark_ptr(rb_objspace_t *objspace, VALUE ptr)
register uintptr_t *bits = GET_HEAP_BITMAP(ptr);
if (MARKED_IN_BITMAP(bits, ptr)) return 0;
MARK_IN_BITMAP(bits, ptr);
- objspace->heap.marked_num++;
return 1;
}
@@ -2921,6 +2923,7 @@ gc_marks(rb_objspace_t *objspace)
objspace->mark_func_data = 0;
gc_prof_mark_timer_start(objspace);
-
objspace->heap.marked_num = 0;
objspace->count++;SET_STACK_END;
Updated by