Implement Process.warmup

[Feature #18885]

For now, the optimizations performed are:

  - Run a major GC
  - Compact the heap
  - Promote all surviving objects to oldgen

Other optimizations may follow.

1 files changed, 27 insertions, 0 deletions

diff --git a/gc.c b/gc.c
index f72818906f..8658660faf 100644
--- a/gc.c
+++ b/gc.c
@@ -9590,6 +9590,26 @@ garbage_collect_with_gvl(rb_objspace_t *objspace, unsigned int reason)
     }
 }
 
+static int
+gc_set_candidate_object_i(void *vstart, void *vend, size_t stride, void *data)
+{
+    rb_objspace_t *objspace = &rb_objspace;
+    VALUE v = (VALUE)vstart;
+    for (; v != (VALUE)vend; v += stride) {
+        switch (BUILTIN_TYPE(v)) {
+          case T_NONE:
+          case T_ZOMBIE:
+            break;
+          default:
+            if (!RVALUE_OLD_P(v) && !RVALUE_WB_UNPROTECTED(v)) {
+                RVALUE_AGE_SET_CANDIDATE(objspace, v);
+            }
+        }
+    }
+
+    return 0;
+}
+
 static VALUE
 gc_start_internal(rb_execution_context_t *ec, VALUE self, VALUE full_mark, VALUE immediate_mark, VALUE immediate_sweep, VALUE compact)
 {
@@ -9617,6 +9637,13 @@ gc_start_internal(rb_execution_context_t *ec, VALUE self, VALUE full_mark, VALUE
     return Qnil;
 }
 
+void
+rb_gc_prepare_heap(void)
+{
+    rb_objspace_each_objects(gc_set_candidate_object_i, NULL);
+    gc_start_internal(NULL, Qtrue, Qtrue, Qtrue, Qtrue, Qtrue);
+}
+
 static int
 gc_is_moveable_obj(rb_objspace_t *objspace, VALUE obj)
 {