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 /*

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

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

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  * published by the Free Software Foundation.

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  * 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.

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

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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.

 // For systems that only commits of memory in a given size (always greater than

 // page size) the base address is required to be aligned to that page size.

 // The actual size requested need not be aligned to that page size, but the size

 // of the reservation passed may be rounded up to this page size. Any fragment

 // (less than the page size) of the actual size at the tail of the request will

 // be committed using OS small 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 size of the tail in bytes of the handled space that needs to be committed

   // using small pages.

   size_t _tail_size;

   // The preferred page size used for commit/uncommit 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;

   // Helper function for committing memory. Commit the given memory range by using

   // _page_size pages as much as possible and the remainder with small sized pages.

   void commit_internal(size_t start_page, size_t end_page);

   // Commit num_pages pages of _page_size size starting from start. All argument

   // checking has been performed.

   void commit_preferred_pages(size_t start_page, size_t end_page);

   // Commit space at the high end of the space that needs to be committed with small

   // sized pages.

   void commit_tail();

   // Uncommit the given memory range.

   void uncommit_internal(size_t start_page, size_t end_page);

   // Pretouch the given memory range.

   void pretouch_internal(size_t start_page, size_t end_page);

   // 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(size_t index) const;

   // Is the given page index the last page?

   bool is_last_page(size_t index) const { return index == (_committed.size() - 1); }

   // Is the given page index the first after last page?

   bool is_after_last_page(size_t index) const;

   // Is the last page only partially covered by this space?

   bool is_last_page_partial() const { return !is_ptr_aligned(_high_boundary, _page_size); }

   // Returns the end address of the given page bounded by the reserved space.

   char* bounded_end_addr(size_t end_page) const;

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

   bool is_area_committed(size_t start_page, size_t size_in_pages) const;

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

   bool is_area_uncommitted(size_t start_page, size_t size_in_pages) const;

   void initialize_with_page_size(ReservedSpace rs, size_t used_size, size_t page_size);

  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(size_t start_page, size_t size_in_pages);

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

   void uncommit(size_t start_page, size_t size_in_pages);

   // Initialize the given reserved space with the given base address and the size

   // actually used.

   // Prefer to commit in page_size chunks.

   G1PageBasedVirtualSpace(ReservedSpace rs, size_t used_size, 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