vm: working on new object-oriented garbage collector

Makefile

@@ -31,6 +31,7 @@ ifdef CONFIG
 endif
 
 DLL_OBJS = $(PLAF_DLL_OBJS) \
+	vm/aging_collector.o \
 	vm/alien.o \
 	vm/arrays.o \
 	vm/bignum.o \
@@ -46,17 +47,21 @@ DLL_OBJS = $(PLAF_DLL_OBJS) \
 	vm/dispatch.o \
 	vm/errors.o \
 	vm/factor.o \
+	vm/full_collector.o \
 	vm/heap.o \
 	vm/image.o \
 	vm/inline_cache.o \
 	vm/io.o \
 	vm/jit.o \
 	vm/math.o \
+	vm/nursery_collector.o \
+	vm/old_space.o \
 	vm/primitives.o \
 	vm/profiler.o \
 	vm/quotations.o \
 	vm/run.o \
 	vm/strings.o \
+	vm/to_tenured_collector.o \
 	vm/tuples.o \
 	vm/utilities.o \
         vm/vm.o \

vm/aging_collector.cpp

@@ -0,0 +1,19 @@
+#include "master.hpp"
+
+namespace factor
+{
+
+aging_collector::aging_collector(factor_vm *myvm_) :
+	copying_collector<aging_space,aging_policy>
+	(myvm_,myvm_->data->aging,aging_policy(myvm_)) {}
+
+void aging_collector::go()
+{
+	trace_roots();
+	trace_contexts();
+	trace_cards(data->tenured);
+	trace_code_heap_roots();
+	cheneys_algorithm();
+}
+
+}

vm/aging_collector.hpp

@@ -0,0 +1,24 @@
+namespace factor
+{
+
+struct aging_policy {
+	factor_vm *myvm;
+	zone *aging, *tenured;
+
+	aging_policy(factor_vm *myvm_) :
+		myvm(myvm_),
+		aging(myvm->data->aging),
+		tenured(myvm->data->tenured) {}
+
+	bool should_copy_p(object *untagged)
+	{
+		return !(aging->contains_p(untagged) || tenured->contains_p(untagged));
+	}
+};
+
+struct aging_collector : copying_collector<aging_space,aging_policy> {
+	aging_collector(factor_vm *myvm_);
+	void go();
+};
+
+}

vm/aging_space.hpp

@@ -0,0 +1,12 @@
+namespace factor
+{
+
+struct aging_space : old_space {
+	aging_space(cell size, cell start) : old_space(size,start) {}
+
+	bool is_nursery_p() { return false; }
+	bool is_aging_p()   { return true; }
+	bool is_tenured_p() { return false; }
+};
+
+}

vm/collector.hpp

@@ -0,0 +1,143 @@
+namespace factor
+{
+
+template<typename TargetGeneration, typename Policy> struct collector {
+	factor_vm *myvm;
+	data_heap *data;
+	gc_state *current_gc;
+	TargetGeneration *target;
+	Policy policy;
+
+	explicit collector(factor_vm *myvm_, TargetGeneration *target_, Policy policy_) :
+		myvm(myvm_),
+		data(myvm_->data),
+		current_gc(myvm_->current_gc),
+		target(target_),
+		policy(policy_) {}
+
+	object *resolve_forwarding(object *untagged)
+	{
+		myvm->check_data_pointer(untagged);
+
+		/* is there another forwarding pointer? */
+		while(untagged->h.forwarding_pointer_p())
+			untagged = untagged->h.forwarding_pointer();
+
+		/* we've found the destination */
+		untagged->h.check_header();
+		return untagged;
+	}
+
+	void trace_handle(cell *handle)
+	{
+		cell pointer = *handle;
+
+		if(immediate_p(pointer)) return;
+
+		object *untagged = myvm->untag<object>(pointer);
+		if(!policy.should_copy_p(untagged))
+			return;
+
+		object *forwarding = resolve_forwarding(untagged);
+
+		if(forwarding == untagged)
+			untagged = promote_object(untagged);
+		else if(policy.should_copy_p(forwarding))
+			untagged = promote_object(forwarding);
+		else
+			untagged = forwarding;
+
+		*handle = RETAG(untagged,TAG(pointer));
+	}
+
+	void trace_slots(object *ptr)
+	{
+		cell *slot = (cell *)ptr;
+		cell *end = (cell *)((cell)ptr + myvm->binary_payload_start(ptr));
+
+		if(slot != end)
+		{
+			slot++;
+			for(; slot < end; slot++) trace_handle(slot);
+		}
+	}
+
+	object *promote_object(object *untagged)
+	{
+		cell size = myvm->untagged_object_size(untagged);
+		object *newpointer = target->allot(size);
+		/* XXX not exception-safe */
+		if(!newpointer) longjmp(current_gc->gc_unwind,1);
+
+		memcpy(newpointer,untagged,size);
+		untagged->h.forward_to(newpointer);
+
+		return newpointer;
+	}
+
+	void trace_stack_elements(segment *region, cell *top)
+	{
+		for(cell *ptr = (cell *)region->start; ptr <= top; ptr++)
+			trace_handle(ptr);
+	}
+
+	void trace_registered_locals()
+	{
+		std::vector<cell>::const_iterator iter = myvm->gc_locals.begin();
+		std::vector<cell>::const_iterator end = myvm->gc_locals.end();
+
+		for(; iter < end; iter++)
+			trace_handle((cell *)(*iter));
+	}
+
+	void trace_registered_bignums()
+	{
+		std::vector<cell>::const_iterator iter = myvm->gc_bignums.begin();
+		std::vector<cell>::const_iterator end = myvm->gc_bignums.end();
+
+		for(; iter < end; iter++)
+		{
+			cell *handle = (cell *)(*iter);
+
+			if(*handle)
+			{
+				*handle |= BIGNUM_TYPE;
+				trace_handle(handle);
+				*handle &= ~BIGNUM_TYPE;
+			}
+		}
+	}
+
+	/* Copy roots over at the start of GC, namely various constants, stacks,
+	the user environment and extra roots registered by local_roots.hpp */
+	void trace_roots()
+	{
+		trace_handle(&myvm->T);
+		trace_handle(&myvm->bignum_zero);
+		trace_handle(&myvm->bignum_pos_one);
+		trace_handle(&myvm->bignum_neg_one);
+
+		trace_registered_locals();
+		trace_registered_bignums();
+
+		for(int i = 0; i < USER_ENV; i++) trace_handle(&myvm->userenv[i]);
+	}
+
+	void trace_contexts()
+	{
+		context *stacks = myvm->stack_chain;
+
+		while(stacks)
+		{
+			trace_stack_elements(stacks->datastack_region,(cell *)stacks->datastack);
+			trace_stack_elements(stacks->retainstack_region,(cell *)stacks->retainstack);
+
+			trace_handle(&stacks->catchstack_save);
+			trace_handle(&stacks->current_callback_save);
+
+			stacks = stacks->next;
+		}
+	}
+};
+
+}

vm/copying_collector.hpp

@@ -0,0 +1,159 @@
+namespace factor
+{
+
+template<typename TargetGeneration, typename Policy>
+struct copying_collector : collector<TargetGeneration,Policy> {
+	cell scan;
+
+	explicit copying_collector(factor_vm *myvm_, TargetGeneration *target_, Policy policy_) :
+		collector<TargetGeneration,Policy>(myvm_,target_,policy_), scan(target_->here) {}
+
+	template<typename SourceGeneration> void trace_objects_between(SourceGeneration *gen, cell scan, cell *end)
+	{
+		while(scan && scan < *end)
+		{
+			this->trace_slots((object *)scan);
+			scan = gen->next_object_after(this->myvm,scan);
+		}
+	}
+
+	template<typename SourceGeneration> void trace_card(SourceGeneration *gen, card *ptr)
+	{
+		cell card_start = this->myvm->card_to_addr(ptr);
+		cell card_scan = card_start + gen->card_offset(card_start);
+		cell card_end = this->myvm->card_to_addr(ptr + 1);
+
+		trace_objects_between(gen,card_scan,&card_end);
+
+		this->myvm->gc_stats.cards_scanned++;
+	}
+
+	template<typename SourceGeneration> void trace_card_deck(SourceGeneration *gen, card_deck *deck, card mask, card unmask)
+	{
+		card *first_card = this->myvm->deck_to_card(deck);
+		card *last_card = this->myvm->deck_to_card(deck + 1);
+
+		u32 *quad_ptr;
+		u32 quad_mask = mask | (mask << 8) | (mask << 16) | (mask << 24);
+
+		for(quad_ptr = (u32 *)first_card; quad_ptr < (u32 *)last_card; quad_ptr++)
+		{
+			if(*quad_ptr & quad_mask)
+			{
+				card *ptr = (card *)quad_ptr;
+
+				for(int card = 0; card < 4; card++)
+				{
+					if(ptr[card] & mask)
+					{
+						trace_card(gen,&ptr[card]);
+						ptr[card] &= ~unmask;
+					}
+				}
+			}
+		}
+
+		this->myvm->gc_stats.decks_scanned++;
+	}
+
+	template<typename SourceGeneration> void trace_cards(SourceGeneration *gen)
+	{
+		u64 start = current_micros();
+
+		card_deck *first_deck = this->myvm->addr_to_deck(gen->start);
+		card_deck *last_deck = this->myvm->addr_to_deck(gen->end);
+
+		card mask, unmask;
+
+		/* if we are collecting the nursery, we care about old->nursery pointers
+		but not old->aging pointers */
+		if(this->current_gc->collecting_nursery_p())
+		{
+			mask = card_points_to_nursery;
+
+			/* after the collection, no old->nursery pointers remain
+			anywhere, but old->aging pointers might remain in tenured
+			space */
+			if(gen->is_tenured_p())
+				unmask = card_points_to_nursery;
+			/* after the collection, all cards in aging space can be
+			cleared */
+			else if(gen->is_aging_p())
+				unmask = card_mark_mask;
+			else
+			{
+				critical_error("bug in trace_gen_cards",0);
+				return;
+			}
+		}
+		/* if we are collecting aging space into tenured space, we care about
+		all old->nursery and old->aging pointers. no old->aging pointers can
+		remain */
+		else if(this->current_gc->collecting_aging_p())
+		{
+			if(this->current_gc->collecting_aging_again)
+			{
+				mask = card_points_to_aging;
+				unmask = card_mark_mask;
+			}
+			/* after we collect aging space into the aging semispace, no
+			old->nursery pointers remain but tenured space might still have
+			pointers to aging space. */
+			else
+			{
+				mask = card_points_to_aging;
+				unmask = card_points_to_nursery;
+			}
+		}
+		else
+		{
+			critical_error("bug in trace_gen_cards",0);
+			return;
+		}
+
+		for(card_deck *ptr = first_deck; ptr < last_deck; ptr++)
+		{
+			if(*ptr & mask)
+			{
+				trace_card_deck(gen,ptr,mask,unmask);
+				*ptr &= ~unmask;
+			}
+		}
+
+		this->myvm->gc_stats.card_scan_time += (current_micros() - start);
+	}
+
+	/* Trace all literals referenced from a code block. Only for aging and nursery collections */
+	void trace_literal_references(code_block *compiled)
+	{
+		this->trace_handle(&compiled->owner);
+		this->trace_handle(&compiled->literals);
+		this->trace_handle(&compiled->relocation);
+	}
+	
+	/* Trace literals referenced from all code blocks. Only for aging and nursery collections */
+	void trace_code_heap_roots()
+	{
+		if(this->current_gc->collecting_gen >= this->myvm->code->youngest_referenced_generation)
+		{
+			unordered_map<code_block *,cell> &remembered_set = this->myvm->code->remembered_set;
+			unordered_map<code_block *,cell>::const_iterator iter = remembered_set.begin();
+			unordered_map<code_block *,cell>::const_iterator end = remembered_set.end();
+	
+			for(; iter != end; iter++)
+			{
+				if(this->current_gc->collecting_gen >= iter->second)
+					trace_literal_references(iter->first);
+			}
+	
+			this->myvm->gc_stats.code_heap_scans++;
+		}
+	}
+
+	void cheneys_algorithm()
+	{
+		trace_objects_between(this->target,scan,&this->target->here);
+	}
+};
+
+}

vm/data_gc.cpp

@@ -399,48 +399,48 @@ void factor_vm::update_dirty_code_blocks()
 }
 
 template<typename Strategy>
-copying_collector<Strategy>::copying_collector(factor_vm *myvm_, old_space *target_)
+cheney_collector<Strategy>::cheney_collector(factor_vm *myvm_, old_space *target_)
 : myvm(myvm_), current_gc(myvm_->current_gc), target(target_)
 {
 	scan = target->here;
 }
 
-template<typename Strategy> Strategy &copying_collector<Strategy>::strategy()
+template<typename Strategy> Strategy &cheney_collector<Strategy>::strategy()
 {
 	return static_cast<Strategy &>(*this);
 }
 
-template<typename Strategy> object *copying_collector<Strategy>::allot(cell size)
+template<typename Strategy> object *cheney_collector<Strategy>::allot(cell size)
 {
 	return target->allot(size);
 }
 
-template<typename Strategy> object *copying_collector<Strategy>::copy_object(object *untagged)
+template<typename Strategy> object *cheney_collector<Strategy>::copy_object(object *untagged)
 {
 	return myvm->promote_object(untagged,strategy());
 }
 
-template<typename Strategy> bool copying_collector<Strategy>::should_copy_p(object *pointer)
+template<typename Strategy> bool cheney_collector<Strategy>::should_copy_p(object *pointer)
 {
 	return strategy().should_copy_p(pointer);
 }
 
-template<typename Strategy> cell copying_collector<Strategy>::trace_next(cell scan)
+template<typename Strategy> cell cheney_collector<Strategy>::trace_next(cell scan)
 {
 	object *obj = (object *)scan;
 	myvm->trace_slots(obj,strategy());
 	return scan + myvm->untagged_object_size(obj);
 }
 
-template<typename Strategy> void copying_collector<Strategy>::go()
+template<typename Strategy> void cheney_collector<Strategy>::go()
 {
 	strategy().copy_reachable_objects(scan,&target->here);
 }
 
-struct nursery_collector : copying_collector<nursery_collector>
+struct nursery_strategy : cheney_collector<nursery_strategy>
 {
-	explicit nursery_collector(factor_vm *myvm_, old_space *target_) :
-		copying_collector<nursery_collector>(myvm_,target_) {}
+	explicit nursery_strategy(factor_vm *myvm_, old_space *target_) :
+		cheney_collector<nursery_strategy>(myvm_,target_) {}
 
 	bool should_copy_p(object *untagged)
 	{
@@ -453,12 +453,12 @@ struct nursery_collector : copying_collector<nursery_collector>
 	}
 };
 
-struct aging_collector : copying_collector<aging_collector>
+struct aging_strategy : cheney_collector<aging_strategy>
 {
 	zone *tenured;
 
-	explicit aging_collector(factor_vm *myvm_, old_space *target_) :
-		copying_collector<aging_collector>(myvm_,target_),
+	explicit aging_strategy(factor_vm *myvm_, old_space *target_) :
+		cheney_collector<aging_strategy>(myvm_,target_),
 		tenured(myvm->data->tenured) {}
 
 	bool should_copy_p(object *untagged)
@@ -475,10 +475,10 @@ struct aging_collector : copying_collector<aging_collector>
 	}
 };
 
-struct aging_again_collector : copying_collector<aging_again_collector>
+struct aging_agian_strategy : cheney_collector<aging_agian_strategy>
 {
-	explicit aging_again_collector(factor_vm *myvm_, old_space *target_) :
-		copying_collector<aging_again_collector>(myvm_,target_) {}
+	explicit aging_agian_strategy(factor_vm *myvm_, old_space *target_) :
+		cheney_collector<aging_agian_strategy>(myvm_,target_) {}
 
 	bool should_copy_p(object *untagged)
 	{
@@ -491,10 +491,10 @@ struct aging_again_collector : copying_collector<aging_again_collector>
 	}
 };
 
-struct tenured_collector : copying_collector<tenured_collector>
+struct tenured_strategy : cheney_collector<tenured_strategy>
 {
-	explicit tenured_collector(factor_vm *myvm_, old_space *target_) :
-		copying_collector<tenured_collector>(myvm_,target_) {}
+	explicit tenured_strategy(factor_vm *myvm_, old_space *target_) :
+		cheney_collector<tenured_strategy>(myvm_,target_) {}
 	
 	bool should_copy_p(object *untagged)
 	{
@@ -513,7 +513,7 @@ struct tenured_collector : copying_collector<tenured_collector>
 
 void factor_vm::collect_nursery()
 {
-	nursery_collector collector(this,data->aging);
+	nursery_strategy collector(this,data->aging);
 
 	trace_roots(collector);
 	trace_contexts(collector);
@@ -531,7 +531,7 @@ void factor_vm::collect_aging()
 	std::swap(data->aging,data->aging_semispace);
 	reset_generation(data->aging);
 
-	aging_collector collector(this,data->aging);
+	aging_strategy collector(this,data->aging);
 
 	trace_roots(collector);
 	trace_contexts(collector);
@@ -545,7 +545,7 @@ void factor_vm::collect_aging()
 
 void factor_vm::collect_aging_again()
 {
-	aging_again_collector collector(this,data->tenured);
+	aging_agian_strategy collector(this,data->tenured);
 
 	trace_roots(collector);
 	trace_contexts(collector);
@@ -571,7 +571,7 @@ void factor_vm::collect_tenured(cell requested_bytes, bool trace_contexts_)
 		reset_generation(data->tenured);
 	}
 
-	tenured_collector collector(this,data->tenured);
+	tenured_strategy collector(this,data->tenured);
 
         trace_roots(collector);
         if(trace_contexts_) trace_contexts(collector);

vm/data_gc.hpp

@@ -63,13 +63,13 @@ struct gc_state {
 	}
 };
 
-template<typename Strategy> struct copying_collector {
+template<typename Strategy> struct cheney_collector {
 	factor_vm *myvm;
 	gc_state *current_gc;
 	old_space *target;
 	cell scan;
 
-	explicit copying_collector(factor_vm *myvm_, old_space *target);
+	explicit cheney_collector(factor_vm *myvm_, old_space *target);
 	Strategy &strategy();
 	object *allot(cell size);
 	cell trace_next(cell scan);

vm/data_heap.cpp

@@ -37,11 +37,11 @@ data_heap::data_heap(factor_vm *myvm, cell young_size_, cell aging_size_, cell t
 
 	cell start = align(seg->start,deck_size);
 
-	tenured = new old_space(tenured_size,start);
-	tenured_semispace = new old_space(tenured_size,tenured->end);
+	tenured = new tenured_space(tenured_size,start);
+	tenured_semispace = new tenured_space(tenured_size,tenured->end);
 
-	aging = new old_space(aging_size,tenured_semispace->end);
-	aging_semispace = new old_space(aging_size,aging->end);
+	aging = new aging_space(aging_size,tenured_semispace->end);
+	aging_semispace = new aging_space(aging_size,aging->end);
 
 	nursery = new zone(young_size,aging_semispace->end);
 

vm/data_heap.hpp

@@ -9,10 +9,10 @@ struct data_heap {
 	segment *seg;
 
 	zone *nursery;
-	old_space *aging;
-	old_space *aging_semispace;
-	old_space *tenured;
-	old_space *tenured_semispace;
+	aging_space *aging;
+	aging_space *aging_semispace;
+	tenured_space *tenured;
+	tenured_space *tenured_semispace;
 
 	char *cards;
 	char *cards_end;

vm/full_collector.cpp

@@ -0,0 +1,17 @@
+#include "master.hpp"
+
+namespace factor
+{
+
+full_collector::full_collector(factor_vm *myvm_, bool trace_contexts_p_) :
+	copying_collector<tenured_space,full_policy>(myvm_,myvm_->data->tenured,full_policy(myvm_)),
+	trace_contexts_p(trace_contexts_p_) {}
+
+void full_collector::go()
+{
+	trace_roots();
+        if(trace_contexts_p) trace_contexts();
+        cheneys_algorithm();
+}
+
+}

vm/full_collector.hpp

@@ -0,0 +1,23 @@
+namespace factor
+{
+
+struct full_policy {
+	factor_vm *myvm;
+	zone *tenured;
+
+	full_policy(factor_vm *myvm_) : myvm(myvm_), tenured(myvm->data->tenured) {}
+
+	bool should_copy_p(object *untagged)
+	{
+		return !tenured->contains_p(untagged);
+	}
+};
+
+struct full_collector : copying_collector<tenured_space,full_policy> {
+	bool trace_contexts_p;
+
+	full_collector(factor_vm *myvm_, bool trace_contexts_p_);
+	void go();
+};
+
+}

vm/master.hpp

@@ -72,6 +72,8 @@ namespace factor
 #include "zone.hpp"
 #include "write_barrier.hpp"
 #include "old_space.hpp"
+#include "aging_space.hpp"
+#include "tenured_space.hpp"
 #include "data_heap.hpp"
 #include "data_gc.hpp"
 #include "debug.hpp"
@@ -87,6 +89,12 @@ namespace factor
 #include "vm.hpp"
 #include "tagged.hpp"
 #include "local_roots.hpp"
+#include "collector.hpp"
+#include "copying_collector.hpp"
+#include "nursery_collector.hpp"
+#include "aging_collector.hpp"
+#include "to_tenured_collector.hpp"
+#include "full_collector.hpp"
 #include "callstack.hpp"
 #include "generic_arrays.hpp"
 #include "arrays.hpp"

vm/nursery_collector.cpp

@@ -0,0 +1,20 @@
+#include "master.hpp"
+
+namespace factor
+{
+
+nursery_collector::nursery_collector(factor_vm *myvm_) :
+	copying_collector<aging_space,nursery_policy>
+	(myvm_,myvm_->data->aging,nursery_policy(myvm_)) {}
+
+void nursery_collector::go()
+{
+	trace_roots();
+	trace_contexts();
+	trace_cards(data->tenured);
+	trace_cards(data->aging);
+	trace_code_heap_roots();
+	cheneys_algorithm();
+}
+
+}

vm/nursery_collector.hpp

@@ -0,0 +1,20 @@
+namespace factor
+{
+
+struct nursery_policy {
+	factor_vm *myvm;
+
+	nursery_policy(factor_vm *myvm_) : myvm(myvm_) {}
+
+	bool should_copy_p(object *untagged)
+	{
+		return myvm->nursery.contains_p(untagged);
+	}
+};
+
+struct nursery_collector : copying_collector<aging_space,nursery_policy> {
+	nursery_collector(factor_vm *myvm_);
+	void go();
+};
+
+}

vm/old_space.cpp

@@ -0,0 +1,54 @@
+#include "master.hpp"
+
+namespace factor
+{
+
+old_space::old_space(cell size_, cell start_) : zone(size_,start_)
+{
+	cell cards_size = size_ >> card_bits;
+	allot_markers = new card[cards_size];
+	allot_markers_end = allot_markers + cards_size;
+}
+
+old_space::~old_space()
+{
+	delete[] allot_markers;
+}
+
+card *old_space::addr_to_allot_marker(object *a)
+{
+	return (card *)((((cell)a - start) >> card_bits) + (cell)allot_markers);
+}
+
+/* we need to remember the first object allocated in the card */
+void old_space::record_allocation(object *obj)
+{
+	card *ptr = addr_to_allot_marker(obj);
+	if(*ptr == invalid_allot_marker)
+		*ptr = ((cell)obj & addr_card_mask);
+}
+
+object *old_space::allot(cell size)
+{
+	if(here + size > end) return NULL;
+
+	object *obj = zone::allot(size);
+	record_allocation(obj);
+	return obj;
+}
+
+void old_space::clear_allot_markers()
+{
+	memset(allot_markers,invalid_allot_marker,size >> card_bits);
+}
+
+cell old_space::next_object_after(factor_vm *myvm, cell scan)
+{
+	cell size = myvm->untagged_object_size((object *)scan);
+	if(scan + size < end)
+		return scan + size;
+	else
+		return NULL;
+}
+
+}

vm/old_space.hpp

@@ -5,58 +5,19 @@ struct old_space : zone {
 	card *allot_markers;
 	card *allot_markers_end;
 
-	old_space(cell size_, cell start_) : zone(size_,start_)
-	{
-		cell cards_size = size_ >> card_bits;
-		allot_markers = new card[cards_size];
-		allot_markers_end = allot_markers + cards_size;
-	}
-
-	~old_space()
-	{
-		delete[] allot_markers;
-	}
-
-	card *addr_to_allot_marker(object *a)
-	{
-		return (card *)((((cell)a - start) >> card_bits) + (cell)allot_markers);
-	}
-
-	/* we need to remember the first object allocated in the card */
-	void record_allocation(object *obj)
-	{
-		card *ptr = addr_to_allot_marker(obj);
-		if(*ptr == invalid_allot_marker)
-			*ptr = ((cell)obj & addr_card_mask);
-	}
+	old_space(cell size_, cell start_);
+	~old_space();
 
 	cell card_offset(cell address)
 	{
 		return allot_markers[(address - start) >> card_bits];
 	}
 
-	object *allot(cell size)
-	{
-		if(here + size > end) return NULL;
-
-		object *obj = zone::allot(size);
-		record_allocation(obj);
-		return obj;
-	}
-
-	void clear_allot_markers()
-	{
-		memset(allot_markers,invalid_allot_marker,size >> card_bits);
-	}
-
-	/* object *next_object_after(object *ptr)
-	{
-		cell size = untagged_object_size(ptr);
-		if((cell)ptr + size < end)
-			return (object *)((cell)ptr + size);
-		else
-			return NULL;
-	} */
+	card *addr_to_allot_marker(object *a);
+	void record_allocation(object *obj);
+	object *allot(cell size);
+	void clear_allot_markers();
+	cell next_object_after(factor_vm *myvm, cell scan);
 };
 
 }

vm/tenured_space.hpp

@@ -0,0 +1,12 @@
+namespace factor
+{
+
+struct tenured_space : old_space {
+	tenured_space(cell size, cell start) : old_space(size,start) {}
+
+	bool is_nursery_p() { return false; }
+	bool is_aging_p()   { return false; }
+	bool is_tenured_p() { return true; }
+};
+
+}

vm/to_tenured_collector.cpp

@@ -0,0 +1,19 @@
+#include "master.hpp"
+
+namespace factor
+{
+
+to_tenured_collector::to_tenured_collector(factor_vm *myvm_) :
+	copying_collector<tenured_space,to_tenured_policy>
+	(myvm_,myvm_->data->tenured,to_tenured_policy(myvm_)) {}
+
+void to_tenured_collector::go()
+{
+	trace_roots();
+	trace_contexts();
+	trace_cards(data->tenured);
+	trace_code_heap_roots();
+	cheneys_algorithm();
+}
+
+}

vm/to_tenured_collector.hpp

@@ -0,0 +1,21 @@
+namespace factor
+{
+
+struct to_tenured_policy {
+	factor_vm *myvm;
+	zone *tenured;
+
+	to_tenured_policy(factor_vm *myvm_) : myvm(myvm_), tenured(myvm->data->tenured) {}
+
+	bool should_copy_p(object *untagged)
+	{
+		return !tenured->contains_p(untagged);
+	}
+};
+
+struct to_tenured_collector : copying_collector<tenured_space,to_tenured_policy> {
+	to_tenured_collector(factor_vm *myvm_);
+	void go();
+};
+
+}

vm/zone.hpp

@@ -9,13 +9,7 @@ struct zone {
 	cell size;
 	cell end;
 
-	cell init_zone(cell size_, cell start_)
-	{
-		size = size_;
-		start = here = start_;
-		end = start_ + size_;
-		return end;
-	}
+	zone(cell size_, cell start_) : start(start_), here(0), size(size_), end(start_ + size_) {}
 
 	inline bool contains_p(object *pointer)
 	{