Oilpan: Reduce sizeof(Persistent) to 16 byte

Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 67 matching lines @@
 SafePointBarrier* ThreadState::s_safePointBarrier = nullptr;
 
 RecursiveMutex& ThreadState::threadAttachMutex()
 {
     AtomicallyInitializedStaticReference(RecursiveMutex, mutex, (new RecursiveMutex));
     return mutex;
 }
 
 ThreadState::ThreadState()
     : m_thread(currentThread())
-    , m_persistents(adoptPtr(new PersistentAnchor()))
+    , m_persistentRegion(adoptPtr(new PersistentRegion()))
     , m_startOfStack(reinterpret_cast<intptr_t*>(StackFrameDepth::getStackStart()))
     , m_endOfStack(reinterpret_cast<intptr_t*>(StackFrameDepth::getStackStart()))
     , m_safePointScopeMarker(nullptr)
     , m_atSafePoint(false)
     , m_interruptors()
     , m_sweepForbidden(false)
     , m_noAllocationCount(0)
     , m_gcForbiddenCount(0)
     , m_vectorBackingHeapIndex(Vector1HeapIndex)
     , m_currentHeapAges(0)
@@ skipping 137 matching lines @@
         // pointers into the heap owned by this thread.
         m_isTerminating = true;
 
         // Set the terminate flag on all heap pages of this thread. This is used to
         // ensure we don't trace pages on other threads that are not part of the
         // thread local GC.
         prepareHeapForTermination();
 
         // Do thread local GC's as long as the count of thread local Persistents
         // changes and is above zero.
-        PersistentAnchor* anchor = m_persistents.get();
         int oldCount = -1;
-        int currentCount = anchor->numberOfPersistents();
+        int currentCount = persistentRegion()->numberOfPersistents();
         ASSERT(currentCount >= 0);
         while (currentCount != oldCount) {
             Heap::collectGarbageForTerminatingThread(this);
             oldCount = currentCount;
-            currentCount = anchor->numberOfPersistents();
+            currentCount = persistentRegion()->numberOfPersistents();
         }
         // We should not have any persistents left when getting to this point,
         // if we have it is probably a bug so adding a debug ASSERT to catch this.
         ASSERT(!currentCount);
         // All of pre-finalizers should be consumed.
         ASSERT(m_preFinalizers.isEmpty());
         RELEASE_ASSERT(gcState() == NoGCScheduled);
 
         // Add pages to the orphaned page pool to ensure any global GCs from this point
         // on will not trace objects on this thread's heaps.
         cleanupPages();
 
         ASSERT(attachedThreads().contains(this));
         attachedThreads().remove(this);
     }
 }
 
 void ThreadState::detach()
 {
     ThreadState* state = current();
     state->cleanup();
     RELEASE_ASSERT(state->gcState() == ThreadState::NoGCScheduled);
     delete state;
     shutdownHeapIfNecessary();
 }
 
 void ThreadState::visitPersistentRoots(Visitor* visitor)
 {
     TRACE_EVENT0("blink_gc", "ThreadState::visitPersistentRoots");
-    {
-        // All threads are at safepoints so this is not strictly necessary.
-        // However we acquire the mutex to make mutation and traversal of this
-        // list symmetrical.
-        MutexLocker locker(globalRootsMutex());
-        globalRoots().tracePersistentNodes(visitor);
-    }
+    crossThreadPersistentRegion().tracePersistentNodes(visitor);
 
     for (ThreadState* state : attachedThreads())
         state->visitPersistents(visitor);
 }
 
 void ThreadState::visitStackRoots(Visitor* visitor)
 {
     TRACE_EVENT0("blink_gc", "ThreadState::visitStackRoots");
     for (ThreadState* state : attachedThreads())
         state->visitStack(visitor);
@@ skipping 66 matching lines @@
         // See the comment above.
         __msan_unpoison(&ptr, sizeof(ptr));
 #endif
         Heap::checkAndMarkPointer(visitor, ptr);
         visitAsanFakeStackForPointer(visitor, ptr);
     }
 }
 
 void ThreadState::visitPersistents(Visitor* visitor)
 {
-    m_persistents->tracePersistentNodes(visitor);
+    m_persistentRegion->tracePersistentNodes(visitor);
     if (m_traceDOMWrappers) {
         TRACE_EVENT0("blink_gc", "V8GCController::traceDOMWrappers");
         m_traceDOMWrappers(m_isolate, visitor);
     }
 }
 
 #if ENABLE(GC_PROFILING)
 const GCInfo* ThreadState::findGCInfo(Address address)
 {
     if (BasePage* page = findPageFromAddress(address))
@@ skipping 148 matching lines @@
 
     MarkingVisitor<Visitor::WeakProcessing> weakProcessingVisitor;
 
     // Perform thread-specific weak processing.
     while (popAndInvokeThreadLocalWeakCallback(&weakProcessingVisitor)) { }
 
     if (isMainThread())
         ScriptForbiddenScope::exit();
 }
 
-PersistentAnchor& ThreadState::globalRoots()
+CrossThreadPersistentRegion& ThreadState::crossThreadPersistentRegion()
 {
-    AtomicallyInitializedStaticReference(PersistentAnchor, anchor, new PersistentAnchor);
-    return anchor;
-}
-
-Mutex& ThreadState::globalRootsMutex()
-{
-    AtomicallyInitializedStaticReference(Mutex, mutex, new Mutex);
-    return mutex;
+    AtomicallyInitializedStaticReference(CrossThreadPersistentRegion, persistentRegion, new CrossThreadPersistentRegion());
+    return persistentRegion;
 }
 
 bool ThreadState::shouldForceMemoryPressureGC()
 {
     // Avoid potential overflow by truncating to Kb.
     size_t currentObjectSizeKb = (Heap::allocatedObjectSize() + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages()) >> 10;
     if (currentObjectSizeKb < 300 * 1024)
         return false;
 
     size_t estimatedLiveObjectSizeKb = Heap::estimatedLiveObjectSize() >> 10;
@@ skipping 943 matching lines @@
         json->beginArray(it->key.ascii().data());
         for (size_t age = 0; age <= maxHeapObjectAge; ++age)
             json->pushInteger(it->value.ages[age]);
         json->endArray();
     }
     TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(TRACE_DISABLED_BY_DEFAULT("blink_gc"), statsName, this, json.release());
 }
 #endif
 
 } // namespace blink