[oilpan]: optimize the way we allocate persistent handles in wrappers.

Source/platform/heap/ThreadState.h

Index: Source/platform/heap/ThreadState.h
diff --git a/Source/platform/heap/ThreadState.h b/Source/platform/heap/ThreadState.h
index 974007726c7e74740324394201e1e49fc7fc1af7..6d1abe9c5899e5d990b353bbe9399d9c5c1c4cfa 100644
--- a/Source/platform/heap/ThreadState.h
+++ b/Source/platform/heap/ThreadState.h
@@ -56,6 +56,7 @@ class HeapContainsCache;
 class HeapObjectHeader;
 class PageMemory;
 class PersistentNode;
+class WrapperPersistentRegion;
 class Visitor;
 class SafePointBarrier;
 class SafePointAwareMutexLocker;
@@ -528,6 +529,14 @@ public:
     BaseHeapPage* contains(void* pointer) { return contains(reinterpret_cast<Address>(pointer)); }
     BaseHeapPage* contains(const void* pointer) { return contains(const_cast<void*>(pointer)); }
 
+    WrapperPersistentRegion* wrapperRoots() const
+    {
+        ASSERT(m_wrapperPersistents);
+        return m_wrapperPersistents;
+    }
+    WrapperPersistentRegion* addWrapperPersistentRegion();
+    void removeWrapperPersistentRegion(WrapperPersistentRegion*);
+
     // List of persistent roots allocated on the given thread.
     PersistentNode* roots() const { return m_persistents.get(); }
 
@@ -652,6 +661,9 @@ private:
     static uint8_t s_mainThreadStateStorage[];
 
     ThreadIdentifier m_thread;
+    WrapperPersistentRegion* m_wrapperPersistents;

[haraken, 2014/09/02 05:22:06]

m_wrapperPersistents => m_usedWrapperPersistents
m_wrapperPersistentRegionPool => m_pooledWrapperPersistents

?

[wibling-chromium, 2014/09/02 11:19:38]

Done. Changed them to

m_liveWrapperPersistents
m_pooledWrapperPersistents

+    WrapperPersistentRegion* m_wrapperPersistentRegionPool;

[haraken, 2014/09/02 05:22:06]

WrapperPersistentRegion is owned by either m_wrapperPersistents or
m_wrapperPersistentRegionPool. Can we use Deque<OwnPtr<WrapperPersistentRegion>>
and avoid implementing insertHead, removeHead etc?

[wibling-chromium, 2014/09/02 11:19:38]

I would prefer to keep it a double-linked list to make internal removal fast.
Ie. there is a good chance for a region to be removed while in the middle of the
list via the removeIfNotLast method.

+    size_t m_wrapperPersistentRegionPoolSize;
     OwnPtr<PersistentNode> m_persistents;
     StackState m_stackState;
     intptr_t* m_startOfStack;