/*+
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 * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.+
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.+
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 *+
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 * This code is free software; you can redistribute it and/or modify it+
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 * under the terms of the GNU General Public License version 2 only, as+
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 * published by the Free Software Foundation.+
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 *+
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 * This code is distributed in the hope that it will be useful, but WITHOUT+
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or+
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License+
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 * version 2 for more details (a copy is included in the LICENSE file that+
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 * accompanied this code).+
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 *+
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 * You should have received a copy of the GNU General Public License version+
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 * 2 along with this work; if not, write to the Free Software Foundation,+
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.+
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 *+
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA+
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 * or visit www.oracle.com if you need additional information or have any+
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 * questions.+
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 *+
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 */+
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+
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#ifndef SHARE_VM_MEMORY_PADDED_HPP+
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#define SHARE_VM_MEMORY_PADDED_HPP+
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+
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#include "memory/allocation.hpp"+
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#include "utilities/align.hpp"+
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#include "utilities/globalDefinitions.hpp"+
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+
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// Bytes needed to pad type to avoid cache-line sharing; alignment should be the+
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// expected cache line size (a power of two).  The first addend avoids sharing+
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// when the start address is not a multiple of alignment; the second maintains+
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// alignment of starting addresses that happen to be a multiple.+
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#define PADDING_SIZE(type, alignment)                           \+
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  ((alignment) + align_up_(sizeof(type), (alignment)))+
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+
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// Templates to create a subclass padded to avoid cache line sharing.  These are+
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// effective only when applied to derived-most (leaf) classes.+
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+
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// When no args are passed to the base ctor.+
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template <class T, size_t alignment = DEFAULT_CACHE_LINE_SIZE>+
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class Padded : public T {+
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 private:+
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  char _pad_buf_[PADDING_SIZE(T, alignment)];+
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};+
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+
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// When either 0 or 1 args may be passed to the base ctor.+
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template <class T, typename Arg1T, size_t alignment = DEFAULT_CACHE_LINE_SIZE>+
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class Padded01 : public T {+
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 public:+
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  Padded01(): T() { }+
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  Padded01(Arg1T arg1): T(arg1) { }+
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 private:+
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  char _pad_buf_[PADDING_SIZE(T, alignment)];+
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};+
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+
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// Super class of PaddedEnd when pad_size != 0.+
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template <class T, size_t pad_size>+
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class PaddedEndImpl : public T {+
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 private:+
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  char _pad_buf[pad_size];+
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};+
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+
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// Super class of PaddedEnd when pad_size == 0.+
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template <class T>+
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class PaddedEndImpl<T, /*pad_size*/ 0> : public T {+
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  // No padding.+
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};+
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+
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#define PADDED_END_SIZE(type, alignment) (align_up_(sizeof(type), (alignment)) - sizeof(type))+
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+
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// More memory conservative implementation of Padded. The subclass adds the+
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// minimal amount of padding needed to make the size of the objects be aligned.+
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// This will help reducing false sharing,+
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// if the start address is a multiple of alignment.+
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template <class T, size_t alignment = DEFAULT_CACHE_LINE_SIZE>+
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class PaddedEnd : public PaddedEndImpl<T, PADDED_END_SIZE(T, alignment)> {+
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  // C++ doesn't allow zero-length arrays. The padding is put in a+
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  // super class that is specialized for the pad_size == 0 case.+
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};+
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+
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// Similar to PaddedEnd, this macro defines a _pad_buf#id field+
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// that is (alignment - size) bytes in size. This macro is used+
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// to add padding in between non-class fields in a class or struct.+
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#define DEFINE_PAD_MINUS_SIZE(id, alignment, size) \+
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          char _pad_buf##id[(alignment) - (size)]+
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+
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// Helper class to create an array of PaddedEnd<T> objects. All elements will+
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// start at a multiple of alignment and the size will be aligned to alignment.+
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template <class T, MEMFLAGS flags, size_t alignment = DEFAULT_CACHE_LINE_SIZE>+
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class PaddedArray {+
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 public:+
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  // Creates an aligned padded array.+
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  // The memory can't be deleted since the raw memory chunk is not returned.+
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  static PaddedEnd<T>* create_unfreeable(uint length);+
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};+
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+
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// Helper class to create an array of references to arrays of primitive types+
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// Both the array of references and the data arrays are aligned to the given+
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// alignment. The allocated memory is zero-filled.+
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template <class T, MEMFLAGS flags, size_t alignment = DEFAULT_CACHE_LINE_SIZE>+
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class Padded2DArray {+
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 public:+
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  // Creates an aligned padded 2D array.+
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  // The memory cannot be deleted since the raw memory chunk is not returned.+
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  static T** create_unfreeable(uint rows, uint columns, size_t* allocation_size = NULL);+
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};+
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+
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// Helper class to create an array of T objects. The array as a whole will+
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// start at a multiple of alignment and its size will be aligned to alignment.+
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template <class T, MEMFLAGS flags, size_t alignment = DEFAULT_CACHE_LINE_SIZE>+
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class PaddedPrimitiveArray {+
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 public:+
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  static T* create_unfreeable(size_t length);+
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};+
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+
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#endif // SHARE_VM_MEMORY_PADDED_HPP+
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