Add RBX_GC_STRESS compile time flag to enable GC stress testing

This allows for defining stress testing of the young and / or mature GC.
This means that the given GC will run as often as possible on every
possible GC checkpoint. This makes it easier to flush out issues due
to for example the GC moving objects.

vm/builtin/class.cpp

@@ -133,6 +133,9 @@ namespace rubinius {
       if(unlikely(state->vm()->allocation_tracking())) {
         new_obj->setup_allocation_site(state, calling_environment);
       }
+#endif
+#ifdef RBX_GC_STRESS
+      state->shared().gc_soon();
 #endif
       return new_obj;
     } else if(!type_info_->allow_user_allocate || kind_of<SingletonClass>(this)) {
@@ -149,6 +152,9 @@ namespace rubinius {
       if(unlikely(state->vm()->allocation_tracking())) {
         new_obj->setup_allocation_site(state, calling_environment);
       }
+#endif
+#ifdef RBX_GC_STRESS
+      state->shared().gc_soon();
 #endif
       return new_obj;
     } else {
@@ -160,6 +166,9 @@ namespace rubinius {
       if(unlikely(state->vm()->allocation_tracking())) {
         new_obj->setup_allocation_site(state, calling_environment);
       }
+#endif
+#ifdef RBX_GC_STRESS
+      state->shared().gc_soon();
 #endif
       return new_obj;
     }

vm/config.h

@@ -6,8 +6,20 @@
 
 #define RBX_STRERROR_BUFSIZE 256
 
-/*
- * Enable this define for some minimal GC debugging
- * #define RBX_GC_DEBUG
- */
+// Enable this define for some minimal GC debugging
+// #define RBX_GC_DEBUG
+
+// Enable for GC stress. This only ensures that the interrupts
+// for a GC are set. Use RBX_GC_STRESS_YOUNG and / or RBX_GC_STRESS_MATURE
+// to run either the young or mature gen on each possibility
+// #define RBX_GC_STRESS
+
+// When stress testing is enabled, forces a young collection every time it
+// is possible. This can be useful to flush out bugs because of moving objects.
+// #define RBX_GC_STRESS_YOUNG
+
+// When stress testing is enabled, forces a mature collection every time it
+// is possible. This can be useful to flush out bugs with reachability etc.
+// #define RBX_GC_STRESS_MATURE
+
 #endif

vm/gc/heap.cpp

@@ -61,7 +61,10 @@ namespace rubinius {
     current_ = start_;
     scan_ = start_;
 #ifdef RBX_GC_DEBUG
+// To heavy when doing GC stress and not necessary
+#ifndef RBX_GC_STRESS
     memset(start_, 0xff, size_);
+#endif
 #endif
   }
 

vm/objectmemory.cpp

@@ -580,7 +580,9 @@ namespace rubinius {
   }
 
   void ObjectMemory::collect_young(GCData& data, YoungCollectStats* stats) {
+#ifndef RBX_GC_STRESS_YOUNG
     collect_young_now = false;
+#endif
 
     timer::Running<1000000> timer(gc_stats.total_young_collection_time,
                                   gc_stats.last_young_collection_time);
@@ -620,8 +622,9 @@ namespace rubinius {
 
     timer::Running<1000000> timer(gc_stats.total_full_collection_time,
                                   gc_stats.last_full_collection_time);
-
+#ifndef RBX_GC_STRESS_MATURE
     collect_mature_now = false;
+#endif
 
     code_manager_.clear_marks();
 

vm/vm.cpp

@@ -197,7 +197,9 @@ namespace rubinius {
     }
 
     obj->init_header(cls, YoungObjectZone, type);
-
+#ifdef RBX_GC_STRESS
+    state.shared().gc_soon();
+#endif
     return obj;
   }
 
@@ -208,6 +210,7 @@ namespace rubinius {
   }
 
   Tuple* VM::new_young_tuple_dirty(size_t fields) {
+    State state(this);
     size_t bytes = Tuple::fields_offset + (sizeof(Object*) * fields);
 
     if(unlikely(bytes > om->large_object_threshold)) {
@@ -217,7 +220,6 @@ namespace rubinius {
     Tuple* tup = local_slab().allocate(bytes).as<Tuple>();
 
     if(unlikely(!tup)) {
-      State state(this);
 
       if(shared.om->refill_slab(&state, local_slab())) {
         tup = local_slab().allocate(bytes).as<Tuple>();
@@ -228,13 +230,17 @@ namespace rubinius {
 
     tup->init_header(G(tuple), YoungObjectZone, Tuple::type);
     tup->full_size_ = bytes;
-
+#ifdef RBX_GC_STRESS
+    state.shared().gc_soon();
+#endif
     return tup;
   }
 
   Object* VM::new_object_typed_mature(Class* cls, size_t bytes, object_type type) {
     State state(this);
-
+#ifdef RBX_GC_STRESS
+    state.shared().gc_soon();
+#endif
     return om->new_object_typed_mature(&state, cls, bytes, type);
   }