32
33 // Virtual space management helper for a virtual space with an OS page allocation
34 // granularity.
35 // (De-)Allocation requests are always OS page aligned by passing a page index
36 // and multiples of pages.
37 // The implementation gives an error when trying to commit or uncommit pages that
38 // have already been committed or uncommitted.
39 class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {
40 friend class VMStructs;
41 private:
42 // Reserved area addresses.
43 char* _low_boundary;
44 char* _high_boundary;
45
46 // The commit/uncommit granularity in bytes.
47 size_t _page_size;
48
49 // Bitmap used for verification of commit/uncommit operations.
50 BitMap _committed;
51
52 // Indicates that the entire space has been committed and pinned in memory,
53 // os::commit_memory() or os::uncommit_memory() have no function.
54 bool _special;
55
56 // Indicates whether the committed space should be executable.
57 bool _executable;
58
59 // Returns the index of the page which contains the given address.
60 uintptr_t addr_to_page_index(char* addr) const;
61 // Returns the address of the given page index.
62 char* page_start(uintptr_t index);
63 // Returns the byte size of the given number of pages.
64 size_t byte_size_for_pages(size_t num);
65
66 // Returns true if the entire area is backed by committed memory.
67 bool is_area_committed(uintptr_t start, size_t size_in_pages) const;
68 // Returns true if the entire area is not backed by committed memory.
69 bool is_area_uncommitted(uintptr_t start, size_t size_in_pages) const;
70
71 public:
72
73 // Commit the given area of pages starting at start being size_in_pages large.
74 MemRegion commit(uintptr_t start, size_t size_in_pages);
75
76 // Uncommit the given area of pages starting at start being size_in_pages large.
77 MemRegion uncommit(uintptr_t start, size_t size_in_pages);
78
79 bool special() const { return _special; }
80
81 // Initialization
82 G1PageBasedVirtualSpace();
83 bool initialize_with_granularity(ReservedSpace rs, size_t page_size);
84
85 // Destruction
86 ~G1PageBasedVirtualSpace();
87
88 // Amount of reserved memory.
89 size_t reserved_size() const;
90 // Memory used in this virtual space.
91 size_t committed_size() const;
92 // Memory left to use/expand in this virtual space.
93 size_t uncommitted_size() const;
94
95 bool contains(const void* p) const;
96
97 MemRegion reserved() {
98 MemRegion x((HeapWord*)_low_boundary, reserved_size() / HeapWordSize);
99 return x;
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32
33 // Virtual space management helper for a virtual space with an OS page allocation
34 // granularity.
35 // (De-)Allocation requests are always OS page aligned by passing a page index
36 // and multiples of pages.
37 // The implementation gives an error when trying to commit or uncommit pages that
38 // have already been committed or uncommitted.
39 class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {
40 friend class VMStructs;
41 private:
42 // Reserved area addresses.
43 char* _low_boundary;
44 char* _high_boundary;
45
46 // The commit/uncommit granularity in bytes.
47 size_t _page_size;
48
49 // Bitmap used for verification of commit/uncommit operations.
50 BitMap _committed;
51
52 // Bitmap used to keep track of which pages are dirty or not for _special
53 // spaces. This is needed because for those spaces the underlying memory
54 // will only be zero filled the first time it is committed. Calls to commit
55 // will use this bitmap and return whether or not the memory is zero filled.
56 BitMap _dirty;
57
58 // Indicates that the entire space has been committed and pinned in memory,
59 // os::commit_memory() or os::uncommit_memory() have no function.
60 bool _special;
61
62 // Indicates whether the committed space should be executable.
63 bool _executable;
64
65 // Returns the index of the page which contains the given address.
66 uintptr_t addr_to_page_index(char* addr) const;
67 // Returns the address of the given page index.
68 char* page_start(uintptr_t index);
69 // Returns the byte size of the given number of pages.
70 size_t byte_size_for_pages(size_t num);
71
72 // Returns true if the entire area is backed by committed memory.
73 bool is_area_committed(uintptr_t start, size_t size_in_pages) const;
74 // Returns true if the entire area is not backed by committed memory.
75 bool is_area_uncommitted(uintptr_t start, size_t size_in_pages) const;
76
77 public:
78
79 // Commit the given area of pages starting at start being size_in_pages large.
80 // Returns true if the given area is zero filled upon completion.
81 bool commit(uintptr_t start, size_t size_in_pages);
82
83 // Uncommit the given area of pages starting at start being size_in_pages large.
84 void uncommit(uintptr_t start, size_t size_in_pages);
85
86 // Initialization
87 G1PageBasedVirtualSpace();
88 bool initialize_with_granularity(ReservedSpace rs, size_t page_size);
89
90 // Destruction
91 ~G1PageBasedVirtualSpace();
92
93 // Amount of reserved memory.
94 size_t reserved_size() const;
95 // Memory used in this virtual space.
96 size_t committed_size() const;
97 // Memory left to use/expand in this virtual space.
98 size_t uncommitted_size() const;
99
100 bool contains(const void* p) const;
101
102 MemRegion reserved() {
103 MemRegion x((HeapWord*)_low_boundary, reserved_size() / HeapWordSize);
104 return x;
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