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 /*

  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1PAGEBASEDVIRTUALSPACE_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1PAGEBASEDVIRTUALSPACE_HPP

 #include "memory/allocation.hpp"

 #include "memory/memRegion.hpp"

 #include "runtime/virtualspace.hpp"

 #include "utilities/bitMap.hpp"

 // Virtual space management helper for a virtual space with an OS page allocation

 // granularity.

 // (De-)Allocation requests are always OS page aligned by passing a page index

 // and multiples of pages.

 // The implementation gives an error when trying to commit or uncommit pages that

 // have already been committed or uncommitted.

 class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {

   friend class VMStructs;

  private:

   // Reserved area addresses.

   char* _low_boundary;

   char* _high_boundary;

   // The commit/uncommit granularity in bytes.

   size_t _page_size;

   // Bitmap used for verification of commit/uncommit operations.

   BitMap _committed;

   // Bitmap used to keep track of which pages are dirty or not for _special

   // spaces. This is needed because for those spaces the underlying memory

   // will only be zero filled the first time it is committed. Calls to commit

   // will use this bitmap and return whether or not the memory is zero filled.

   BitMap _dirty;

   // Indicates that the entire space has been committed and pinned in memory,

   // os::commit_memory() or os::uncommit_memory() have no function.

   bool _special;

   // Indicates whether the committed space should be executable.

   bool _executable;

   // Returns the index of the page which contains the given address.

   uintptr_t  addr_to_page_index(char* addr) const;

   // Returns the address of the given page index.

   char*  page_start(uintptr_t index);

   // Returns the byte size of the given number of pages.

   size_t byte_size_for_pages(size_t num);

   // Returns true if the entire area is backed by committed memory.

   bool is_area_committed(uintptr_t start, size_t size_in_pages) const;

   // Returns true if the entire area is not backed by committed memory.

   bool is_area_uncommitted(uintptr_t start, size_t size_in_pages) const;

  public:

   // Commit the given area of pages starting at start being size_in_pages large.

   // Returns true if the given area is zero filled upon completion.

   bool commit(uintptr_t start, size_t size_in_pages);

   // Uncommit the given area of pages starting at start being size_in_pages large.

   void uncommit(uintptr_t start, size_t size_in_pages);

   // Initialization

   G1PageBasedVirtualSpace();

   bool initialize_with_granularity(ReservedSpace rs, size_t page_size);

   // Destruction

   ~G1PageBasedVirtualSpace();

   // Amount of reserved memory.

   size_t reserved_size() const;

   // Memory used in this virtual space.

   size_t committed_size() const;

   // Memory left to use/expand in this virtual space.

   size_t uncommitted_size() const;

   bool contains(const void* p) const;

   MemRegion reserved() {

     MemRegion x((HeapWord*)_low_boundary, reserved_size() / HeapWordSize);

     return x;

   }

   void release();

   void check_for_contiguity() PRODUCT_RETURN;

   // Debugging

   void print_on(outputStream* out) PRODUCT_RETURN;

   void print();

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1PAGEBASEDVIRTUALSPACE_HPP