Changeset 155317 in webkit for trunk/Source/JavaScriptCore/heap/Heap.cpp

Timestamp:

Sep 8, 2013, 5:11:57 PM (12 years ago)

Author:

[email protected]

Message:

Calculating the size of the Heap should not require walking over it
​https://bugs.webkit.org/show_bug.cgi?id=120910

Reviewed by Geoffrey Garen.

Currently Heap::size() is O(sizeof(Heap)). This is too expensive to
call during a collection. We should keep a count of visited and copied
bytes as each collection progresses so as to avoid re-walking the Heap
at the end of collection.

• heap/GCThreadSharedData.cpp:

(JSC::GCThreadSharedData::childBytesVisited):
(JSC::GCThreadSharedData::childBytesCopied):

• heap/GCThreadSharedData.h:
• heap/Heap.cpp:

(JSC::Heap::Heap):
(JSC::Heap::markRoots):
(JSC::Heap::sizeAfterCollect):
(JSC::Heap::collect):

• heap/Heap.h:
• heap/SlotVisitor.cpp:

(JSC::SlotVisitor::SlotVisitor):
(JSC::SlotVisitor::reset):

• heap/SlotVisitor.h:

(JSC::SlotVisitor::bytesVisited):
(JSC::SlotVisitor::bytesCopied):

• heap/SlotVisitorInlines.h:

(JSC::SlotVisitor::internalAppend):
(JSC::SlotVisitor::copyLater):

File:

• trunk/Source/JavaScriptCore/heap/Heap.cpp (modified) (4 diffs)

trunk/Source/JavaScriptCore/heap/Heap.cpp

@@ -252 +252 @@
     , m_bytesAllocated(0)
     , m_bytesAbandoned(0)
+    , m_totalBytesVisited(0)
+    , m_totalBytesCopied(0)
     , m_operationInProgress(NoOperation)
     , m_blockAllocator()
@@ -592 +594 @@
 #endif
 
+    m_totalBytesVisited = visitor.bytesVisited();
+    m_totalBytesCopied = visitor.bytesCopied();
+#if ENABLE(PARALLEL_GC)
+    m_totalBytesVisited += m_sharedData.childBytesVisited();
+    m_totalBytesCopied += m_sharedData.childBytesCopied();
+#endif
+
     visitor.reset();
 #if ENABLE(PARALLEL_GC)
@@ -635 +644 @@
 }
 
+size_t Heap::sizeAfterCollect()
+{
+    // The result here may not agree with the normal Heap::size(). 
+    // This is due to the fact that we only count live copied bytes
+    // rather than all used (including dead) copied bytes, thus it's 
+    // always the case that m_totalBytesCopied <= m_storageSpace.size(). 
+    ASSERT(m_totalBytesCopied <= m_storageSpace.size());
+    return m_totalBytesVisited + m_totalBytesCopied + extraSize();
+}
+
 size_t Heap::protectedGlobalObjectCount()
 {
@@ -799 +818 @@
     }
     
-    size_t currentHeapSize = size();
+    size_t currentHeapSize = sizeAfterCollect();
     if (Options::gcMaxHeapSize() && currentHeapSize > Options::gcMaxHeapSize())
         HeapStatistics::exitWithFailure();