src/share/vm/runtime/os.cpp

rev 6634 : 8048895: Back out JDK-8027915

@@ -1301,19 +1301,28 @@
   // The very lower end of the stack
   address stack_limit = thread->stack_base() - thread->stack_size();
   return (sp > (stack_limit + reserved_area));
 }
 
-size_t os::page_size_for_region(size_t region_size, size_t min_pages) {
+size_t os::page_size_for_region(size_t region_min_size, size_t region_max_size,
+                                uint min_pages)
+{
   assert(min_pages > 0, "sanity");
   if (UseLargePages) {
-    const size_t max_page_size = region_size / min_pages;
+    const size_t max_page_size = region_max_size / min_pages;
+
+    for (unsigned int i = 0; _page_sizes[i] != 0; ++i) {
+      const size_t sz = _page_sizes[i];
+      const size_t mask = sz - 1;
+      if ((region_min_size & mask) == 0 && (region_max_size & mask) == 0) {
+        // The largest page size with no fragmentation.
+        return sz;
+      }
 
-    for (size_t i = 0; _page_sizes[i] != 0; ++i) {
-      const size_t page_size = _page_sizes[i];
-      if (page_size <= max_page_size && is_size_aligned(region_size, page_size)) {
-        return page_size;
+      if (sz <= max_page_size) {
+        // The largest page size that satisfies the min_pages requirement.
+        return sz;
       }
     }
   }
 
   return vm_page_size();

@@ -1537,65 +1546,5 @@
     return to;
   }
   return result;
 }
 #endif
-
-/////////////// Unit tests ///////////////
-
-#ifndef PRODUCT
-
-#define assert_eq(a,b) assert(a == b, err_msg(SIZE_FORMAT " != " SIZE_FORMAT, a, b))
-
-class TestOS : AllStatic {
-  static size_t small_page_size() {
-    return os::vm_page_size();
-  }
-
-  static size_t large_page_size() {
-    const size_t large_page_size_example = 4 * M;
-    return os::page_size_for_region(large_page_size_example, 1);
-  }
-
-  static void test_page_size_for_region() {
-    if (UseLargePages) {
-      const size_t small_page = small_page_size();
-      const size_t large_page = large_page_size();
-
-      if (large_page > small_page) {
-        size_t num_small_pages_in_large = large_page / small_page;
-        size_t page = os::page_size_for_region(large_page, num_small_pages_in_large);
-
-        assert_eq(page, small_page);
-      }
-    }
-  }
-
-  static void test_page_size_for_region_alignment() {
-    if (UseLargePages) {
-      const size_t small_page = small_page_size();
-      const size_t large_page = large_page_size();
-      if (large_page > small_page) {
-        const size_t unaligned_region = large_page + 17;
-        size_t page = os::page_size_for_region(unaligned_region, 1);
-        assert_eq(page, small_page);
-
-        const size_t num_pages = 5;
-        const size_t aligned_region = large_page * num_pages;
-        page = os::page_size_for_region(aligned_region, num_pages);
-        assert_eq(page, large_page);
-      }
-    }
-  }
-
- public:
-  static void run_tests() {
-    test_page_size_for_region();
-    test_page_size_for_region_alignment();
-  }
-};
-
-void TestOS_test() {
-  TestOS::run_tests();
-}
-
-#endif // PRODUCT