don't need to sweep rest.

`transient_heap_evacuate()` disables GC using `rb_gc_disable()`
to prohibt GC invocation because of new allocation for evacuated
memory. However, `rb_gc_disable()` sweep all rest of unswept pages.
We don't need to cancel lazy sweep so this patch introduce
`rb_gc_disable_no_rest()` which doesn't cancel lazy sweep.

gc.c

@@ -8938,6 +8938,15 @@ rb_gc_enable(void)
     return old ? Qtrue : Qfalse;
 }
 
+VALUE
+rb_gc_disable_no_rest(void)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    int old = dont_gc;
+    dont_gc = TRUE;
+    return old ? Qtrue : Qfalse;
+}
+
 /*
  *  call-seq:
  *     GC.disable    -> true or false
@@ -8954,12 +8963,8 @@ VALUE
 rb_gc_disable(void)
 {
     rb_objspace_t *objspace = &rb_objspace;
-    int old = dont_gc;
-
     gc_rest(objspace);
-
+    return rb_gc_disable_no_rest();
-    dont_gc = TRUE;
-    return old ? Qtrue : Qfalse;
 }
 
 static int

gc.h

@@ -94,6 +94,8 @@ const char *rb_obj_info(VALUE obj);
 const char *rb_raw_obj_info(char *buff, const int buff_size, VALUE obj);
 void rb_obj_info_dump(VALUE obj);
 
+VALUE rb_gc_disable_no_rest(void);
+
 struct rb_thread_struct;
 
 RUBY_SYMBOL_EXPORT_BEGIN

transient_heap.c

@@ -730,7 +730,7 @@ transient_heap_evacuate(void *dmy)
         if (TRANSIENT_HEAP_DEBUG >= 1) fprintf(stderr, "!! transient_heap_evacuate: skip while transient_heap_marking\n");
     }
     else {
-        VALUE gc_disabled = rb_gc_disable();
+        VALUE gc_disabled = rb_gc_disable_no_rest();
         struct transient_heap_block* block;
 
         if (TRANSIENT_HEAP_DEBUG >= 1) {