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comparison src/share/vm/memory/padded.hpp @ 12029:9766f73e770d

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8022880: False sharing between PSPromotionManager instances Summary: Pad the PSPromotionManager instances in the manager array. Reviewed-by: brutisso, jmasa
author stefank
date Fri, 31 May 2013 14:32:44 +0200
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children d7070f371770
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12009:39127bb12d32 12029:9766f73e770d
1 /*
2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_MEMORY_PADDED_HPP
26 #define SHARE_VM_MEMORY_PADDED_HPP
27
28 #include "memory/allocation.hpp"
29 #include "utilities/globalDefinitions.hpp"
30
31 // Bytes needed to pad type to avoid cache-line sharing; alignment should be the
32 // expected cache line size (a power of two). The first addend avoids sharing
33 // when the start address is not a multiple of alignment; the second maintains
34 // alignment of starting addresses that happen to be a multiple.
35 #define PADDING_SIZE(type, alignment) \
36 ((alignment) + align_size_up_(sizeof(type), alignment))
37
38 // Templates to create a subclass padded to avoid cache line sharing. These are
39 // effective only when applied to derived-most (leaf) classes.
40
41 // When no args are passed to the base ctor.
42 template <class T, size_t alignment = DEFAULT_CACHE_LINE_SIZE>
43 class Padded : public T {
44 private:
45 char _pad_buf_[PADDING_SIZE(T, alignment)];
46 };
47
48 // When either 0 or 1 args may be passed to the base ctor.
49 template <class T, typename Arg1T, size_t alignment = DEFAULT_CACHE_LINE_SIZE>
50 class Padded01 : public T {
51 public:
52 Padded01(): T() { }
53 Padded01(Arg1T arg1): T(arg1) { }
54 private:
55 char _pad_buf_[PADDING_SIZE(T, alignment)];
56 };
57
58 // Super class of PaddedEnd when pad_size != 0.
59 template <class T, size_t pad_size>
60 class PaddedEndImpl : public T {
61 private:
62 char _pad_buf[pad_size];
63 };
64
65 // Super class of PaddedEnd when pad_size == 0.
66 template <class T>
67 class PaddedEndImpl<T, /*pad_size*/ 0> : public T {
68 // No padding.
69 };
70
71 #define PADDED_END_SIZE(type, alignment) (align_size_up_(sizeof(type), alignment) - sizeof(type))
72
73 // More memory conservative implementation of Padded. The subclass adds the
74 // minimal amount of padding needed to make the size of the objects be aligned.
75 // This will help reducing false sharing,
76 // if the start address is a multiple of alignment.
77 template <class T, size_t alignment = DEFAULT_CACHE_LINE_SIZE>
78 class PaddedEnd : public PaddedEndImpl<T, PADDED_END_SIZE(T, alignment)> {
79 // C++ don't allow zero-length arrays. The padding is put in a
80 // super class that is specialized for the pad_size == 0 case.
81 };
82
83 // Helper class to create an array of PaddedEnd<T> objects. All elements will
84 // start at a multiple of alignment and the size will be aligned to alignment.
85 template <class T, MEMFLAGS flags, size_t alignment = DEFAULT_CACHE_LINE_SIZE>
86 class PaddedArray {
87 public:
88 // Creates an aligned padded array.
89 // The memory can't be deleted since the raw memory chunk is not returned.
90 static PaddedEnd<T>* create_unfreeable(uint length);
91 };
92
93 #endif // SHARE_VM_MEMORY_PADDED_HPP