JavaScriptCore-1097.3.tar.gz

[apple/javascriptcore.git] / heap / BlockAllocator.h

diff --git a/heap/BlockAllocator.h b/heap/BlockAllocator.h
new file mode 100644 (file)
index 0000000..2ae72ec
--- /dev/null
+++ b/heap/BlockAllocator.h
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2012 Apple 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:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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 with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef BlockAllocator_h
+#define BlockAllocator_h
+
+#include "GCActivityCallback.h"
+#include <wtf/DoublyLinkedList.h>
+#include <wtf/Forward.h>
+#include <wtf/Threading.h>
+
+namespace JSC {
+
+class HeapBlock;
+
+// Simple allocator to reduce VM cost by holding onto blocks of memory for
+// short periods of time and then freeing them on a secondary thread.
+
+class BlockAllocator {
+public:
+    BlockAllocator();
+    ~BlockAllocator();
+
+    HeapBlock* allocate();
+    void deallocate(HeapBlock*);
+
+private:
+    void waitForRelativeTimeWhileHoldingLock(double relative);
+    void waitForRelativeTime(double relative);
+
+    void blockFreeingThreadMain();
+    static void blockFreeingThreadStartFunc(void* heap);
+
+    void releaseFreeBlocks();
+
+    DoublyLinkedList<HeapBlock> m_freeBlocks;
+    size_t m_numberOfFreeBlocks;
+    bool m_isCurrentlyAllocating;
+    bool m_blockFreeingThreadShouldQuit;
+    Mutex m_freeBlockLock;
+    ThreadCondition m_freeBlockCondition;
+    ThreadIdentifier m_blockFreeingThread;
+};
+
+inline HeapBlock* BlockAllocator::allocate()
+{
+    MutexLocker locker(m_freeBlockLock);
+    m_isCurrentlyAllocating = true;
+    if (!m_numberOfFreeBlocks) {
+        ASSERT(m_freeBlocks.isEmpty());
+        return 0;
+    }
+
+    ASSERT(!m_freeBlocks.isEmpty());
+    m_numberOfFreeBlocks--;
+    return m_freeBlocks.removeHead();
+}
+
+inline void BlockAllocator::deallocate(HeapBlock* block)
+{
+    {
+        MutexLocker locker(m_freeBlockLock);
+        m_freeBlocks.push(block);
+        m_numberOfFreeBlocks++;
+    }
+    if (!GCActivityCallback::s_shouldCreateGCTimer);
+        releaseFreeBlocks();
+}
+
+} // namespace JSC
+
+#endif // BlockAllocator_h