1853       return empty_range();
1854     }
1855     return AddrRange(from, to - from);
1856   }
1857 };
1858 
1859 ////////////////////////////////////////////////////////////////////////////
1860 // shared memory bookkeeping
1861 //
1862 // the os::reserve_memory() API and friends hand out different kind of memory, depending
1863 // on need and circumstances. Memory may be allocated with mmap() or with shmget/shmat.
1864 //
1865 // But these memory types have to be treated differently. For example, to uncommit
1866 // mmap-based memory, msync(MS_INVALIDATE) is needed, to uncommit shmat-based memory,
1867 // disclaim64() is needed.
1868 //
1869 // Therefore we need to keep track of the allocated memory segments and their
1870 // properties.
1871 
1872 // ShmBkBlock: base class for all blocks in the shared memory bookkeeping
1873 class ShmBkBlock {
1874 
1875   ShmBkBlock* _next;
1876 
1877 protected:
1878 
1879   AddrRange _range;
1880   const size_t _pagesize;
1881   const bool _pinned;
1882 
1883 public:
1884 
1885   ShmBkBlock(AddrRange range, size_t pagesize, bool pinned)
1886     : _range(range), _pagesize(pagesize), _pinned(pinned) , _next(NULL) {
1887 
1888     assert(_pagesize == SIZE_4K || _pagesize == SIZE_64K || _pagesize == SIZE_16M, "invalid page size");
1889     assert(!_range.is_empty(), "invalid range");
1890   }
1891 
1892   virtual void print(outputStream* st) const {
1893     st->print("0x%p ... 0x%p (%llu) - %d %s pages - %s",

1853       return empty_range();
1854     }
1855     return AddrRange(from, to - from);
1856   }
1857 };
1858 
1859 ////////////////////////////////////////////////////////////////////////////
1860 // shared memory bookkeeping
1861 //
1862 // the os::reserve_memory() API and friends hand out different kind of memory, depending
1863 // on need and circumstances. Memory may be allocated with mmap() or with shmget/shmat.
1864 //
1865 // But these memory types have to be treated differently. For example, to uncommit
1866 // mmap-based memory, msync(MS_INVALIDATE) is needed, to uncommit shmat-based memory,
1867 // disclaim64() is needed.
1868 //
1869 // Therefore we need to keep track of the allocated memory segments and their
1870 // properties.
1871 
1872 // ShmBkBlock: base class for all blocks in the shared memory bookkeeping
1873 class ShmBkBlock : public CHeapObj<mtInternal> {
1874 
1875   ShmBkBlock* _next;
1876 
1877 protected:
1878 
1879   AddrRange _range;
1880   const size_t _pagesize;
1881   const bool _pinned;
1882 
1883 public:
1884 
1885   ShmBkBlock(AddrRange range, size_t pagesize, bool pinned)
1886     : _range(range), _pagesize(pagesize), _pinned(pinned) , _next(NULL) {
1887 
1888     assert(_pagesize == SIZE_4K || _pagesize == SIZE_64K || _pagesize == SIZE_16M, "invalid page size");
1889     assert(!_range.is_empty(), "invalid range");
1890   }
1891 
1892   virtual void print(outputStream* st) const {
1893     st->print("0x%p ... 0x%p (%llu) - %d %s pages - %s",