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

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 * 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.

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#ifndef SHARE_VM_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP

#define SHARE_VM_GC_G1_G1PAGEBASEDVIRTUALSPACE_HPP

#include "memory/allocation.hpp"

#include "memory/memRegion.hpp"

#include "memory/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_G1_G1PAGEBASEDVIRTUALSPACE_HPP