Introduce conservative sweeping.

src/spaces.cc

 // Copyright 2006-2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 39 matching lines @@
   Initialize(space->bottom(), space->top(), NULL);
 }
 
 
 HeapObjectIterator::HeapObjectIterator(PagedSpace* space,
                                        HeapObjectCallback size_func) {
   Initialize(space->bottom(), space->top(), size_func);
 }
 
 
-HeapObjectIterator::HeapObjectIterator(PagedSpace* space, Address start) {
-  Initialize(start, space->top(), NULL);
-}
-
-
-HeapObjectIterator::HeapObjectIterator(PagedSpace* space, Address start,
-                                       HeapObjectCallback size_func) {
-  Initialize(start, space->top(), size_func);
-}
-
-
 HeapObjectIterator::HeapObjectIterator(Page* page,
                                        HeapObjectCallback size_func) {
   Initialize(page->ObjectAreaStart(), page->AllocationTop(), size_func);
 }
 
 
 void HeapObjectIterator::Initialize(Address cur, Address end,
                                     HeapObjectCallback size_f) {
   cur_addr_ = cur;
   end_addr_ = end;
   end_page_ = Page::FromAllocationTop(end);
   size_func_ = size_f;
   Page* p = Page::FromAllocationTop(cur_addr_);
   cur_limit_ = (p == end_page_) ? end_addr_ : p->AllocationTop();
 
+  if (!p->IsFlagSet(Page::IS_CONTINIOUS)) {
+    cur_addr_ = Marking::FirstLiveObject(cur_addr_, cur_limit_);
+    if (cur_addr_ > cur_limit_) cur_addr_ = cur_limit_;
+  }
+
 #ifdef DEBUG
   Verify();
 #endif
 }
 
 
 HeapObject* HeapObjectIterator::FromNextPage() {
   if (cur_addr_ == end_addr_) return NULL;
 
   Page* cur_page = Page::FromAllocationTop(cur_addr_);
   cur_page = cur_page->next_page();
   ASSERT(cur_page->is_valid());
 
   cur_addr_ = cur_page->ObjectAreaStart();
   cur_limit_ = (cur_page == end_page_) ? end_addr_ : cur_page->AllocationTop();
 
+  if (!cur_page->IsFlagSet(Page::IS_CONTINIOUS)) {
+    cur_addr_ = Marking::FirstLiveObject(cur_addr_, cur_limit_);
+    if (cur_addr_ > cur_limit_) cur_addr_ = cur_limit_;
+  }
+
   if (cur_addr_ == end_addr_) return NULL;
   ASSERT(cur_addr_ < cur_limit_);
 #ifdef DEBUG
   Verify();
 #endif
   return FromCurrentPage();
 }
 
 
+void HeapObjectIterator::AdvanceUsingMarkbits() {
+  HeapObject* obj = HeapObject::FromAddress(cur_addr_);
+  int obj_size = (size_func_ == NULL) ? obj->Size() : size_func_(obj);
+  ASSERT_OBJECT_SIZE(obj_size);
+  cur_addr_ = Marking::NextLiveObject(obj,
+                                      obj_size,
+                                      cur_limit_);
+  if (cur_addr_ > cur_limit_) cur_addr_ = cur_limit_;
+}
+
+
 #ifdef DEBUG
 void HeapObjectIterator::Verify() {
   Page* p = Page::FromAllocationTop(cur_addr_);
   ASSERT(p == Page::FromAllocationTop(cur_limit_));
   ASSERT(p->Offset(cur_addr_) <= p->Offset(cur_limit_));
 }
 #endif
 
 
 // -----------------------------------------------------------------------------
@@ skipping 659 matching lines @@
     if (above_allocation_top) {
       // We don't care what's above the allocation top.
     } else {
       Address top = current_page->AllocationTop();
       if (current_page == top_page) {
         ASSERT(top == allocation_info_.top);
         // The next page will be above the allocation top.
         above_allocation_top = true;
       }
 
-      // It should be packed with objects from the bottom to the top.
-      Address current = current_page->ObjectAreaStart();
-      while (current < top) {
-        HeapObject* object = HeapObject::FromAddress(current);
+      HeapObjectIterator it(current_page, NULL);
+      Address end_of_previous_object = current_page->ObjectAreaStart();
+      for(HeapObject* object = it.next(); object != NULL; object = it.next()) {
+        ASSERT(end_of_previous_object <= object->address());
 
         // The first word should be a map, and we expect all map pointers to
         // be in map space.
         Map* map = object->map();
         ASSERT(map->IsMap());
         ASSERT(Heap::map_space()->Contains(map));
 
         // Perform space-specific object verification.
         VerifyObject(object);
 
+        if (object->IsCodeCache() && ((uint32_t*)object->address())[2] == 0x2) {
+          current_page->PrintMarkbits();
+        }
+
         // The object itself should look OK.
         object->Verify();
 
         // All the interior pointers should be contained in the heap and
         // have page regions covering intergenerational references should be
         // marked dirty.
         int size = object->Size();
         object->IterateBody(map->instance_type(), size, visitor);
 
-        current += size;
+        ASSERT(object->address() + size <= top);
+        end_of_previous_object = object->address() + size;
       }
-
-      // The allocation pointer should not be in the middle of an object.
-      ASSERT(current == top);
     }
 
     current_page = current_page->next_page();
   }
 }
 #endif
 
 
 // -----------------------------------------------------------------------------
 // NewSpace implementation
@@ skipping 837 matching lines @@
   ASSERT(bytes <= InitialCapacity());
   Address limit = allocation_info_.limit;
   Address top = allocation_info_.top;
   return limit - top >= bytes;
 }
 
 
 void PagedSpace::FreePages(Page* prev, Page* last) {
   if (last == AllocationTopPage()) {
     // Pages are already at the end of used pages.
+    // Just clean them.

[Erik Corry, 2011/01/19 13:46:48]

How are they cleaned?

[Vyacheslav Egorov (Chromium), 2011/01/20 16:40:21]

Done.

+    Page* p = prev == NULL ? first_page_ : prev->next_page();
+    Page* end_page = last->next_page();
+    do {
+      p->SetFlag(Page::IS_CONTINIOUS);
+      p = p->next_page();
+    } while (p != end_page);
     return;
   }
 
   Page* first = NULL;
 
   // Remove pages from the list.
   if (prev == NULL) {
     first = first_page_;
     first_page_ = last->next_page();
   } else {
     first = prev->next_page();
     prev->set_next_page(last->next_page());
   }
 
   // Attach it after the last page.
   last_page_->set_next_page(first);
   last_page_ = last;
   last->set_next_page(NULL);
 
   // Clean them up.
   do {
     first->InvalidateWatermark(true);
     first->SetAllocationWatermark(first->ObjectAreaStart());
     first->SetCachedAllocationWatermark(first->ObjectAreaStart());
     first->SetRegionMarks(Page::kAllRegionsCleanMarks);
+    first->SetFlag(Page::IS_CONTINIOUS);
     first->markbits()->Clear();
     first = first->next_page();
-  } while (first != NULL);
+  } while (first->is_valid());
 }
 
 
 void PagedSpace::PrepareForMarkCompact(bool will_compact) {
   ASSERT(!will_compact);
 }
 
 
 bool PagedSpace::ReserveSpace(int bytes) {
   Address limit = allocation_info_.limit;
@@ skipping 58 matching lines @@
 
       if (obj->address() >= p->AllocationWatermark()) {
         // There should be no hole between the allocation watermark
         // and allocated object address.
         // Memory above the allocation watermark was not swept and
         // might contain garbage pointers to new space.
         ASSERT(obj->address() == p->AllocationWatermark());
         p->SetAllocationWatermark(obj->address() + size_in_bytes);
       }
 
+      if (!p->IsFlagSet(Page::IS_CONTINIOUS)) {
+        // This page is not continious so we have to mark objects
+        // that should be visited by HeapObjectIterator.
+        ASSERT(!Marking::IsMarked(obj));
+        Marking::SetMark(obj);
+      }
+
       return obj;
     }
   }
 
   // Free list allocation failed and there is no next page.  Fail if we have
   // hit the old generation size limit that should cause a garbage
   // collection.
   if (!Heap::always_allocate() && Heap::OldGenerationAllocationLimitReached()) {
     return NULL;
   }
@@ skipping 670 matching lines @@
   for (HeapObject* obj = obj_it.next(); obj != NULL; obj = obj_it.next()) {
     if (obj->IsCode()) {
       Code* code = Code::cast(obj);
       code_kind_statistics[code->kind()] += code->Size();
     }
   }
 }
 #endif  // DEBUG
 
 } }  // namespace v8::internal