1 /*
   2  * Copyright (c) 2014, 2015, 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_G1_G1PAGEBASEDVIRTUALSPACE_HPP
  26 #define SHARE_VM_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "memory/memRegion.hpp"
  30 #include "memory/virtualspace.hpp"
  31 #include "utilities/bitMap.hpp"
  32 
  33 class 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.
  47 class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {
  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   uintptr_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_ptr_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   bool contains(const void* p) const;
 140 
 141   MemRegion reserved() {
 142     MemRegion x((HeapWord*)_low_boundary, reserved_size() / HeapWordSize);
 143     return x;
 144   }
 145 
 146   void check_for_contiguity() PRODUCT_RETURN;
 147 
 148   // Debugging
 149   void print_on(outputStream* out) PRODUCT_RETURN;
 150   void print();
 151 };
 152 
 153 #endif // SHARE_VM_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP