1/*
2 * Copyright (c) 2014, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25#ifndef SHARE_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP
26#define SHARE_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP
27
28#include "memory/memRegion.hpp"
29#include "memory/virtualspace.hpp"
30#include "utilities/align.hpp"
31#include "utilities/bitMap.hpp"
32
33class WorkGang;
34
35// Virtual space management helper for a virtual space with an OS page allocation
36// granularity.
37// (De-)Allocation requests are always OS page aligned by passing a page index
38// and multiples of pages.
39// For systems that only commits of memory in a given size (always greater than
40// page size) the base address is required to be aligned to that page size.
41// The actual size requested need not be aligned to that page size, but the size
42// of the reservation passed may be rounded up to this page size. Any fragment
43// (less than the page size) of the actual size at the tail of the request will
44// be committed using OS small pages.
45// The implementation gives an error when trying to commit or uncommit pages that
46// have already been committed or uncommitted.
47class G1PageBasedVirtualSpace {
48 friend class VMStructs;
49 private:
50 // Reserved area addresses.
51 char* _low_boundary;
52 char* _high_boundary;
53
54 // The size of the tail in bytes of the handled space that needs to be committed
55 // using small pages.
56 size_t _tail_size;
57
58 // The preferred page size used for commit/uncommit in bytes.
59 size_t _page_size;
60
61 // Bitmap used for verification of commit/uncommit operations.
62 CHeapBitMap _committed;
63
64 // Bitmap used to keep track of which pages are dirty or not for _special
65 // spaces. This is needed because for those spaces the underlying memory
66 // will only be zero filled the first time it is committed. Calls to commit
67 // will use this bitmap and return whether or not the memory is zero filled.
68 CHeapBitMap _dirty;
69
70 // Indicates that the entire space has been committed and pinned in memory,
71 // os::commit_memory() or os::uncommit_memory() have no function.
72 bool _special;
73
74 // Indicates whether the committed space should be executable.
75 bool _executable;
76
77 // Helper function for committing memory. Commit the given memory range by using
78 // _page_size pages as much as possible and the remainder with small sized pages.
79 void commit_internal(size_t start_page, size_t end_page);
80 // Commit num_pages pages of _page_size size starting from start. All argument
81 // checking has been performed.
82 void commit_preferred_pages(size_t start_page, size_t end_page);
83 // Commit space at the high end of the space that needs to be committed with small
84 // sized pages.
85 void commit_tail();
86
87 // Uncommit the given memory range.
88 void uncommit_internal(size_t start_page, size_t end_page);
89
90 // Pretouch the given memory range.
91 void pretouch_internal(size_t start_page, size_t end_page);
92
93 // Returns the index of the page which contains the given address.
94 size_t addr_to_page_index(char* addr) const;
95 // Returns the address of the given page index.
96 char* page_start(size_t index) const;
97
98 // Is the given page index the last page?
99 bool is_last_page(size_t index) const { return index == (_committed.size() - 1); }
100 // Is the given page index the first after last page?
101 bool is_after_last_page(size_t index) const;
102 // Is the last page only partially covered by this space?
103 bool is_last_page_partial() const { return !is_aligned(_high_boundary, _page_size); }
104 // Returns the end address of the given page bounded by the reserved space.
105 char* bounded_end_addr(size_t end_page) const;
106
107 // Returns true if the entire area is backed by committed memory.
108 bool is_area_committed(size_t start_page, size_t size_in_pages) const;
109 // Returns true if the entire area is not backed by committed memory.
110 bool is_area_uncommitted(size_t start_page, size_t size_in_pages) const;
111
112 void initialize_with_page_size(ReservedSpace rs, size_t used_size, size_t page_size);
113 public:
114
115 // Commit the given area of pages starting at start being size_in_pages large.
116 // Returns true if the given area is zero filled upon completion.
117 bool commit(size_t start_page, size_t size_in_pages);
118
119 // Uncommit the given area of pages starting at start being size_in_pages large.
120 void uncommit(size_t start_page, size_t size_in_pages);
121
122 void pretouch(size_t start_page, size_t size_in_pages, WorkGang* pretouch_gang = NULL);
123
124 // Initialize the given reserved space with the given base address and the size
125 // actually used.
126 // Prefer to commit in page_size chunks.
127 G1PageBasedVirtualSpace(ReservedSpace rs, size_t used_size, size_t page_size);
128
129 // Destruction
130 ~G1PageBasedVirtualSpace();
131
132 // Amount of reserved memory.
133 size_t reserved_size() const;
134 // Memory used in this virtual space.
135 size_t committed_size() const;
136 // Memory left to use/expand in this virtual space.
137 size_t uncommitted_size() const;
138
139 void commit_and_set_special();
140
141 bool contains(const void* p) const;
142
143 MemRegion reserved() {
144 MemRegion x((HeapWord*)_low_boundary, reserved_size() / HeapWordSize);
145 return x;
146 }
147
148 void check_for_contiguity() PRODUCT_RETURN;
149
150 // Debugging
151 void print_on(outputStream* out) PRODUCT_RETURN;
152 void print();
153};
154
155#endif // SHARE_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP
156