JavaScriptCore-1097.3.tar.gz

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

diff --git a/heap/BlockAllocator.cpp b/heap/BlockAllocator.cpp
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+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "BlockAllocator.h"
+
+#include "MarkedBlock.h"
+#include <wtf/CurrentTime.h>
+
+namespace JSC {
+
+BlockAllocator::BlockAllocator()
+    : m_numberOfFreeBlocks(0)
+    , m_isCurrentlyAllocating(false)
+    , m_blockFreeingThreadShouldQuit(false)
+    , m_blockFreeingThread(GCActivityCallback::s_shouldCreateGCTimer ?
+        createThread(blockFreeingThreadStartFunc, this, "JavaScriptCore::BlockFree") : 0)
+{
+    ASSERT(m_blockFreeingThread || !GCActivityCallback::s_shouldCreateGCTimer);
+}
+
+BlockAllocator::~BlockAllocator()
+{
+    releaseFreeBlocks();
+    {
+        MutexLocker locker(m_freeBlockLock);
+        m_blockFreeingThreadShouldQuit = true;
+        m_freeBlockCondition.broadcast();
+    }
+    if (GCActivityCallback::s_shouldCreateGCTimer)
+        waitForThreadCompletion(m_blockFreeingThread);
+}
+
+void BlockAllocator::releaseFreeBlocks()
+{
+    while (true) {
+        MarkedBlock* block;
+        {
+            MutexLocker locker(m_freeBlockLock);
+            if (!m_numberOfFreeBlocks)
+                block = 0;
+            else {
+                // FIXME: How do we know this is a MarkedBlock? It could be a CopiedBlock.
+                block = static_cast<MarkedBlock*>(m_freeBlocks.removeHead());
+                ASSERT(block);
+                m_numberOfFreeBlocks--;
+            }
+        }
+        
+        if (!block)
+            break;
+        
+        MarkedBlock::destroy(block);
+    }
+}
+
+void BlockAllocator::waitForRelativeTimeWhileHoldingLock(double relative)
+{
+    if (m_blockFreeingThreadShouldQuit)
+        return;
+    m_freeBlockCondition.timedWait(m_freeBlockLock, currentTime() + relative);
+}
+
+void BlockAllocator::waitForRelativeTime(double relative)
+{
+    // If this returns early, that's fine, so long as it doesn't do it too
+    // frequently. It would only be a bug if this function failed to return
+    // when it was asked to do so.
+    
+    MutexLocker locker(m_freeBlockLock);
+    waitForRelativeTimeWhileHoldingLock(relative);
+}
+
+void BlockAllocator::blockFreeingThreadStartFunc(void* blockAllocator)
+{
+    static_cast<BlockAllocator*>(blockAllocator)->blockFreeingThreadMain();
+}
+
+void BlockAllocator::blockFreeingThreadMain()
+{
+    while (!m_blockFreeingThreadShouldQuit) {
+        // Generally wait for one second before scavenging free blocks. This
+        // may return early, particularly when we're being asked to quit.
+        waitForRelativeTime(1.0);
+        if (m_blockFreeingThreadShouldQuit)
+            break;
+        
+        if (m_isCurrentlyAllocating) {
+            m_isCurrentlyAllocating = false;
+            continue;
+        }
+
+        // Now process the list of free blocks. Keep freeing until half of the
+        // blocks that are currently on the list are gone. Assume that a size_t
+        // field can be accessed atomically.
+        size_t currentNumberOfFreeBlocks = m_numberOfFreeBlocks;
+        if (!currentNumberOfFreeBlocks)
+            continue;
+        
+        size_t desiredNumberOfFreeBlocks = currentNumberOfFreeBlocks / 2;
+        
+        while (!m_blockFreeingThreadShouldQuit) {
+            MarkedBlock* block;
+            {
+                MutexLocker locker(m_freeBlockLock);
+                if (m_numberOfFreeBlocks <= desiredNumberOfFreeBlocks)
+                    block = 0;
+                else {
+                    // FIXME: How do we know this is a MarkedBlock? It could be a CopiedBlock.
+                    block = static_cast<MarkedBlock*>(m_freeBlocks.removeHead());
+                    ASSERT(block);
+                    m_numberOfFreeBlocks--;
+                }
+            }
+            
+            if (!block)
+                break;
+            
+            MarkedBlock::destroy(block);
+        }
+    }
+}
+
+} // namespace JSC