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

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index 7dc044028e5de8affae544cb3b1ff6a89ce59461..103d16c05fb44cb9aedd1383e50780e35e415511 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -265,7 +265,6 @@ private:
     ThreadCondition m_resume;
 };
 
-
 BaseHeapPage::BaseHeapPage(PageMemory* storage, const GCInfo* gcInfo, ThreadState* state)
     : m_storage(storage)
     , m_gcInfo(gcInfo)
@@ -292,6 +291,9 @@ template<> struct InitializeHeaps<0> {
 
 ThreadState::ThreadState()
     : m_thread(currentThread())
+    , m_wrapperPersistents(new WrapperPersistentRegion())
+    , m_wrapperPersistentRegionPool(0)
+    , m_wrapperPersistentRegionPoolSize(0)
     , m_persistents(adoptPtr(new PersistentAnchor()))
     , m_startOfStack(reinterpret_cast<intptr_t*>(getStackStart()))
     , m_endOfStack(reinterpret_cast<intptr_t*>(getStackStart()))
@@ -330,6 +332,10 @@ ThreadState::~ThreadState()
     for (int i = 0; i < NumberOfHeaps; i++)
         delete m_heaps[i];
     deleteAllValues(m_interruptors);
+    while (m_wrapperPersistents) {

[Mads Ager (chromium), 2014/09/01 13:52:46]

How about regions that are in the pool? Should we delete those here as well?

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

That seems like a good idea:) Fixed.

+        WrapperPersistentRegion* region = WrapperPersistentRegion::removeHead(&m_wrapperPersistents);
+        delete region;
+    }
     **s_threadSpecific = 0;
 }
 
@@ -561,6 +567,7 @@ void ThreadState::visitStack(Visitor* visitor)
 void ThreadState::visitPersistents(Visitor* visitor)
 {
     m_persistents->trace(visitor);
+    m_wrapperPersistents->trace(visitor);
 }
 
 bool ThreadState::checkAndMarkPointer(Visitor* visitor, Address address)
@@ -680,6 +687,35 @@ bool ThreadState::popAndInvokeWeakPointerCallback(Visitor* visitor)
     return m_weakCallbackStack->popAndInvokeCallback<WeaknessProcessing>(&m_weakCallbackStack, visitor);
 }
 
+WrapperPersistentRegion* ThreadState::addWrapperPersistentRegion()
+{
+    WrapperPersistentRegion* region;
+    if (m_wrapperPersistentRegionPoolSize) {
+        region = WrapperPersistentRegion::removeHead(&m_wrapperPersistentRegionPool);
+        m_wrapperPersistentRegionPoolSize--;
+    } else {
+        region = new WrapperPersistentRegion();
+    }
+    ASSERT(region);
+    WrapperPersistentRegion::insertHead(&m_wrapperPersistents, region);
+    return region;
+}
+
+void ThreadState::removeWrapperPersistentRegion(WrapperPersistentRegion* region)
+{
+    ASSERT(!region->count());
+    if (!region->removeIfNotLast(&m_wrapperPersistents))
+        return;
+
+    // Region was removed, ie. it is was not the last region in the list.

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

it is was => it was

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

Done.

+    if (m_wrapperPersistentRegionPoolSize < 2) {

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

What does the '< 2' check mean?

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

It means we will only keep at most two regions in the pool. This is to avoid
having too large a memory overhead.

+        WrapperPersistentRegion::insertHead(&m_wrapperPersistentRegionPool, region);
+        m_wrapperPersistentRegionPoolSize++;
+    } else {
+        delete region;
+    }
+}
+
 PersistentNode* ThreadState::globalRoots()
 {
     AtomicallyInitializedStatic(PersistentNode*, anchor = new PersistentAnchor);