src/share/vm/runtime/os.cpp

rev 7514 : 8066875: VirtualSpace does not use large pages

*** 1413,1422 ****
--- 1413,1434 ----
    }
  
    return vm_page_size();
  }
  
+ size_t os::largest_page_size_less_than(size_t sz) {
+   if (UseLargePages) {
+     // The page sizes are sorted descendingly.
+     for (size_t i = 0; _page_sizes[i] != 0; ++i) {
+       if (_page_sizes[i] <= sz) {
+         return _page_sizes[i];
+       }
+     }
+   }
+   return vm_page_size();
+ }
+ 
  #ifndef PRODUCT
  void os::trace_page_sizes(const char* str, const size_t* page_sizes, int count)
  {
    if (TracePageSizes) {
      tty->print("%s: ", str);
*** 1690,1703 ****
--- 1702,1747 ----
          assert_eq(page, large_page);
        }
      }
    }
  
+   static void test_largest_page_size_less_than() {
+     if (UseLargePages) {
+       // Given exact page size, should return that page size
+       for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
+         size_t expected = os::_page_sizes[i];
+         size_t actual = os::largest_page_size_less_than(expected);
+         assert_eq(expected, actual);
+       }
+ 
+       // Given slightly larger size than a page size, return the page size
+       for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
+         size_t expected = os::_page_sizes[i];
+         size_t actual = os::largest_page_size_less_than(expected + 17);
+         assert_eq(expected, actual);
+       }
+ 
+       // Given a slightly smaller size than a page size,
+       // return the next smaller page size
+       if (os::_page_sizes[1] > os::_page_sizes[0]) {
+         size_t expected = os::_page_sizes[0];
+         size_t actual = os::largest_page_size_less_than(os::_page_sizes[1] - 17);
+         assert_eq(actual, expected);
+       }
+ 
+       // Return small page size for values less than a small page
+       size_t small_page = small_page_size();
+       size_t actual = os::largest_page_size_less_than(small_page - 17);
+       assert_eq(small_page, actual);
+     }
+   }
+ 
   public:
    static void run_tests() {
      test_page_size_for_region();
      test_page_size_for_region_alignment();
+     test_largest_page_size_less_than();
    }
  };
  
  void TestOS_test() {
    TestOS::run_tests();