src/share/vm/memory/virtualspace.cpp

@@ -119,11 +119,13 @@
     return;
   }
 
   // If OS doesn't support demand paging for large page memory, we need
   // to use reserve_memory_special() to reserve and pin the entire region.
-  bool special = large && !os::can_commit_large_page_memory();
+  // If there is a backing file directory for this VirtualSpace then whether largepages are allocated is upto the filesystem the dir resides in.
+  // So we ignore the UseLargePages flag in this case.
+  bool special = (_backingFileDir == NULL) && (large && !os::can_commit_large_page_memory());
   char* base = NULL;
 
   if (special) {
 
     base = os::reserve_memory_special(size, alignment, requested_address, executable);

@@ -150,18 +152,31 @@
       }
     }
   }
 
   if (base == NULL) {
+
+          // If '_backingFileDir' variable is not null, the memory should be backed by a file.
+          // The code path taken in the 'if' block below is very similar to the 'else' block with only different being that it uses a file descriptor (fd) for mmap() calls.
+          // reserve_memory_with_backing_file() encapsulates the different cases which are handled in the 'else' block
+          if (_backingFileDir != NULL) {
+      base = os::reserve_memory_with_backing_file(size, requested_address, alignment, _backingFileDir);
+
+      if (requested_address != 0 && failed_to_reserve_as_requested(base, requested_address, size, false)) {
+        // OS ignored requested address. Try different address.
+        base = NULL;
+        return;
+      }
+    }
+    else {
     // Optimistically assume that the OSes returns an aligned base pointer.
     // When reserving a large address range, most OSes seem to align to at
     // least 64K.
 
     // If the memory was requested at a particular address, use
     // os::attempt_reserve_memory_at() to avoid over mapping something
     // important.  If available space is not detected, return NULL.
-
     if (requested_address != 0) {
       base = os::attempt_reserve_memory_at(size, requested_address);
       if (failed_to_reserve_as_requested(base, requested_address, size, false)) {
         // OS ignored requested address. Try different address.
         base = NULL;

@@ -188,10 +203,11 @@
         assert(_base == NULL, "should be");
         return;
       }
     }
   }
+  }
   // Done
   _base = base;
   _size = size;
   _alignment = alignment;
 }

@@ -316,11 +332,11 @@
     release();
   }
 
   // If OS doesn't support demand paging for large page memory, we need
   // to use reserve_memory_special() to reserve and pin the entire region.
-  bool special = large && !os::can_commit_large_page_memory();
+  bool special = _backingFileDir == NULL && large && !os::can_commit_large_page_memory();
   char* base = NULL;
 
   if (PrintCompressedOopsMode && Verbose) {
     tty->print("Trying to allocate at address " PTR_FORMAT " heap of size " SIZE_FORMAT_HEX ".\n",
                p2i(requested_address), size);

@@ -347,10 +363,24 @@
         tty->cr();
         tty->print_cr("Reserve regular memory without large pages.");
       }
     }
 
+    // If '_backingFileDir' variable is not null, the memory should be backed by a file.
+        // The code path taken in the 'if' block below is very similar to the 'else' block with only different being that it uses a file descriptor (fd) for mmap() calls.
+        // reserve_memory_with_backing_file() encapsulates the two cases which are handled in the 'else' block
+    if (_backingFileDir != NULL) {
+      base = os::reserve_memory_with_backing_file(size, requested_address, alignment, _backingFileDir);
+      if (requested_address != 0 && failed_to_reserve_as_requested(base, requested_address, size, false)) {
+        // OS ignored requested address. Try different address.
+        base = NULL;
+        return;
+      }
+      _special = true;
+    }
+    else {
+    
     // Optimistically assume that the OSes returns an aligned base pointer.
     // When reserving a large address range, most OSes seem to align to at
     // least 64K.
 
     // If the memory was requested at a particular address, use

@@ -361,10 +391,11 @@
       base = os::attempt_reserve_memory_at(size, requested_address);
     } else {
       base = os::reserve_memory(size, NULL, alignment);
     }
   }
+  }
   if (base == NULL) { return; }
 
   // Done
   _base = base;
   _size = size;

@@ -564,16 +595,16 @@
       initialize(size + noaccess_prefix, alignment, large, NULL, false);
     }
   }
 }
 
-ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t alignment, bool large) : ReservedSpace() {
+ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t alignment, bool large, const char* backingFSforHeap) : ReservedSpace() {
 
   if (size == 0) {
     return;
   }
-
+  _backingFileDir= backingFSforHeap;
   // Heap size should be aligned to alignment, too.
   guarantee(is_size_aligned(size, alignment), "set by caller");
 
   if (UseCompressedOops) {
     initialize_compressed_heap(size, alignment, large);