1 /*
2  * Copyright (c) 2014, 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_GC_IMPLEMENTATION_G1_G1PAGEBASEDVIRTUALSPACE_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1PAGEBASEDVIRTUALSPACE_HPP
27 
28 #include "memory/allocation.hpp"
29 #include "memory/memRegion.hpp"
30 #include "runtime/virtualspace.hpp"
31 #include "utilities/bitMap.hpp"
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 // For systems that only commits of memory in a given size (always greater than
38 // page size) the base address is required to be aligned to that page size.
39 // The actual size requested need not be aligned to that page size, but the size
40 // of the reservation passed may be rounded up to this page size. Any fragment
41 // (less than the page size) of the actual size at the tail of the request will
42 // be committed using OS small pages.
43 // The implementation gives an error when trying to commit or uncommit pages that
44 // have already been committed or uncommitted.
45 class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {
46   friend class VMStructs;
47  private:
48   // Reserved area addresses.
49   char* _low_boundary;
50   char* _high_boundary;
51 
52   // The size of the tail in bytes of the handled space that needs to be committed
53   // using small pages.
54   size_t _tail_size;
55 
56   // The preferred page size used for commit/uncommit in bytes.
57   size_t _page_size;
58 
59   // Bitmap used for verification of commit/uncommit operations.
60   BitMap _committed;
61 
62   // Bitmap used to keep track of which pages are dirty or not for _special
63   // spaces. This is needed because for those spaces the underlying memory
64   // will only be zero filled the first time it is committed. Calls to commit
65   // will use this bitmap and return whether or not the memory is zero filled.
66   BitMap _dirty;
67 
68   // Indicates that the entire space has been committed and pinned in memory,
69   // os::commit_memory() or os::uncommit_memory() have no function.
70   bool _special;
71 
72   // Indicates whether the committed space should be executable.
73   bool _executable;
74 
75   // Helper function for committing memory. Commit the given memory range by using
76   // _page_size pages as much as possible and the remainder with small sized pages.
77   void commit_internal(size_t start_page, size_t end_page);
78   // Commit num_pages pages of _page_size size starting from start. All argument
79   // checking has been performed.
80   void commit_preferred_pages(size_t start_page, size_t end_page);
81   // Commit space at the high end of the space that needs to be committed with small
82   // sized pages.
83   void commit_tail();
84 
85   // Uncommit the given memory range.
86   void uncommit_internal(size_t start_page, size_t end_page);
87 
88   // Pretouch the given memory range.
89   void pretouch_internal(size_t start_page, size_t end_page);
90 
91   // Returns the index of the page which contains the given address.
92   uintptr_t  addr_to_page_index(char* addr) const;
93   // Returns the address of the given page index.
94   char*  page_start(size_t index) const;
95 
96   // Is the given page index the last page?
is_last_page(size_t index) const97   bool is_last_page(size_t index) const { return index == (_committed.size() - 1); }
98   // Is the given page index the first after last page?
99   bool is_after_last_page(size_t index) const;
100   // Is the last page only partially covered by this space?
is_last_page_partial() const101   bool is_last_page_partial() const { return !is_ptr_aligned(_high_boundary, _page_size); }
102   // Returns the end address of the given page bounded by the reserved space.
103   char* bounded_end_addr(size_t end_page) const;
104 
105   // Returns true if the entire area is backed by committed memory.
106   bool is_area_committed(size_t start_page, size_t size_in_pages) const;
107   // Returns true if the entire area is not backed by committed memory.
108   bool is_area_uncommitted(size_t start_page, size_t size_in_pages) const;
109 
110   void initialize_with_page_size(ReservedSpace rs, size_t used_size, size_t page_size);
111  public:
112 
113   // Commit the given area of pages starting at start being size_in_pages large.
114   // Returns true if the given area is zero filled upon completion.
115   bool commit(size_t start_page, size_t size_in_pages);
116 
117   // Uncommit the given area of pages starting at start being size_in_pages large.
118   void uncommit(size_t start_page, size_t size_in_pages);
119 
120   // Initialize the given reserved space with the given base address and the size
121   // actually used.
122   // Prefer to commit in page_size chunks.
123   G1PageBasedVirtualSpace(ReservedSpace rs, size_t used_size, size_t page_size);
124 
125   // Destruction
126   ~G1PageBasedVirtualSpace();
127 
128   // Amount of reserved memory.
129   size_t reserved_size() const;
130   // Memory used in this virtual space.
131   size_t committed_size() const;
132   // Memory left to use/expand in this virtual space.
133   size_t uncommitted_size() const;
134 
135   bool contains(const void* p) const;
136 
reserved()137   MemRegion reserved() {
138     MemRegion x((HeapWord*)_low_boundary, reserved_size() / HeapWordSize);
139     return x;
140   }
141 
142   void release();
143 
144   void check_for_contiguity() PRODUCT_RETURN;
145 
146   // Debugging
147   void print_on(outputStream* out) PRODUCT_RETURN;
148   void print();
149 };
150 
151 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1PAGEBASEDVIRTUALSPACE_HPP
152