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

/*
 * 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
Commit	Line	Data
6fe7ccc8 A	1	/*
	2	* Copyright (C) 2012 Apple Inc. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	7	* 1. Redistributions of source code must retain the above copyright
	8	* notice, this list of conditions and the following disclaimer.
	9	* 2. Redistributions in binary form must reproduce the above copyright
	10	* notice, this list of conditions and the following disclaimer in the
	11	* documentation and/or other materials provided with the distribution.
	12	*
	13	* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
	14	* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
	15	* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	16	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
	17	* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	18	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	19	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	20	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	21	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	22	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
	23	* THE POSSIBILITY OF SUCH DAMAGE.
	24	*/
	25
	26	#ifndef BlockAllocator_h
	27	#define BlockAllocator_h
	28
	29	#include "GCActivityCallback.h"
	30	#include <wtf/DoublyLinkedList.h>
	31	#include <wtf/Forward.h>
	32	#include <wtf/Threading.h>
	33
	34	namespace JSC {
	35
	36	class HeapBlock;
	37
	38	// Simple allocator to reduce VM cost by holding onto blocks of memory for
	39	// short periods of time and then freeing them on a secondary thread.
	40
	41	class BlockAllocator {
	42	public:
	43	BlockAllocator();
	44	~BlockAllocator();
	45
	46	HeapBlock* allocate();
	47	void deallocate(HeapBlock*);
	48
	49	private:
	50	void waitForRelativeTimeWhileHoldingLock(double relative);
	51	void waitForRelativeTime(double relative);
	52
	53	void blockFreeingThreadMain();
	54	static void blockFreeingThreadStartFunc(void* heap);
	55
	56	void releaseFreeBlocks();
	57
	58	DoublyLinkedList<HeapBlock> m_freeBlocks;
	59	size_t m_numberOfFreeBlocks;
	60	bool m_isCurrentlyAllocating;
	61	bool m_blockFreeingThreadShouldQuit;
	62	Mutex m_freeBlockLock;
	63	ThreadCondition m_freeBlockCondition;
	64	ThreadIdentifier m_blockFreeingThread;
65	};
66
67	inline HeapBlock* BlockAllocator::allocate()
68	{
69	MutexLocker locker(m_freeBlockLock);
70	m_isCurrentlyAllocating = true;
71	if (!m_numberOfFreeBlocks) {
72	ASSERT(m_freeBlocks.isEmpty());
73	return 0;
74	}
75
76	ASSERT(!m_freeBlocks.isEmpty());
77	m_numberOfFreeBlocks--;
78	return m_freeBlocks.removeHead();
79	}
80
81	inline void BlockAllocator::deallocate(HeapBlock* block)
82	{
83	{
84	MutexLocker locker(m_freeBlockLock);
85	m_freeBlocks.push(block);
86	m_numberOfFreeBlocks++;
87	}
88	if (!GCActivityCallback::s_shouldCreateGCTimer);
89	releaseFreeBlocks();
90	}
91
92	} // namespace JSC
93
94	#endif // BlockAllocator_h