the begginning

utils/common/poolallocator.h

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+/* Copyright (C) 2014 InfiniDB, Inc.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; version 2 of
+   the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA. */
+
+/******************************************************************************************
+* $Id$
+*
+******************************************************************************************/
+
+/* This allocator is an attempt to consolidate small allocations and
+   deallocations to boost performance and reduce mem fragmentation. */
+
+#ifndef POOLALLOCATOR_H_
+#define POOLALLOCATOR_H_
+
+#include <unistd.h>
+#include <stdint.h>
+#include <vector>
+#include <map>
+#include <boost/shared_array.hpp>
+
+namespace utils {
+
+class PoolAllocator
+{
+public:
+	static const unsigned DEFAULT_WINDOW_SIZE = 4096 * 40;  // should be an integral # of pages
+
+	explicit PoolAllocator(unsigned windowSize = DEFAULT_WINDOW_SIZE, bool isTmpSpace = false) :
+		allocSize(windowSize),
+		tmpSpace(isTmpSpace),
+		capacityRemaining(0),
+		memUsage(0),
+		nextAlloc(0) { }
+	PoolAllocator(const PoolAllocator &p) :
+		allocSize(p.allocSize),
+		tmpSpace(p.tmpSpace),
+		capacityRemaining(0),
+		memUsage(0),
+		nextAlloc(0) { }
+	virtual ~PoolAllocator() {}
+
+	PoolAllocator & operator=(const PoolAllocator &);
+
+	void *allocate(uint64_t size);
+	void deallocate(void *p);
+	void deallocateAll();
+
+	inline uint64_t getMemUsage() const { return memUsage; }
+	unsigned getWindowSize() const { return allocSize; }
+
+private:
+	void newBlock();
+
+	unsigned allocSize;
+	std::vector<boost::shared_array<uint8_t> > mem;
+	bool tmpSpace;
+	unsigned capacityRemaining;
+	uint64_t memUsage;
+	uint8_t *nextAlloc;
+	
+	struct OOBMemInfo {
+		boost::shared_array<uint8_t> mem;
+		uint64_t size;
+	};
+	typedef std::map<void *, OOBMemInfo> OutOfBandMap;
+	OutOfBandMap oob;  // for mem chunks bigger than the window size; these can be dealloc'd
+};
+
+}
+
+#endif