--- a/jdk/src/share/classes/java/nio/Bits.java	Fri Oct 15 12:10:32 2010 +0100
+++ b/jdk/src/share/classes/java/nio/Bits.java	Fri Oct 15 15:09:37 2010 +0100
@@ -622,7 +622,7 @@
     // initialization if it is launched with "-XX:MaxDirectMemorySize=<size>".
     private static volatile long maxMemory = VM.maxDirectMemory();
     private static volatile long reservedMemory;
-    private static volatile long usedMemory;
+    private static volatile long totalCapacity;
     private static volatile long count;
     private static boolean memoryLimitSet = false;
 
@@ -630,15 +630,17 @@
     // freed.  They allow the user to control the amount of direct memory
     // which a process may access.  All sizes are specified in bytes.
     static void reserveMemory(long size, int cap) {
-
         synchronized (Bits.class) {
             if (!memoryLimitSet && VM.isBooted()) {
                 maxMemory = VM.maxDirectMemory();
                 memoryLimitSet = true;
             }
-            if (size <= maxMemory - reservedMemory) {
+            // -XX:MaxDirectMemorySize limits the total capacity rather than the
+            // actual memory usage, which will differ when buffers are page
+            // aligned.
+            if (cap <= maxMemory - totalCapacity) {
                 reservedMemory += size;
-                usedMemory += cap;
+                totalCapacity += cap;
                 count++;
                 return;
             }
@@ -652,10 +654,10 @@
             Thread.currentThread().interrupt();
         }
         synchronized (Bits.class) {
-            if (reservedMemory + size > maxMemory)
+            if (totalCapacity + cap > maxMemory)
                 throw new OutOfMemoryError("Direct buffer memory");
             reservedMemory += size;
-            usedMemory += cap;
+            totalCapacity += cap;
             count++;
         }
 
@@ -664,7 +666,7 @@
     static synchronized void unreserveMemory(long size, int cap) {
         if (reservedMemory > 0) {
             reservedMemory -= size;
-            usedMemory -= cap;
+            totalCapacity -= cap;
             count--;
             assert (reservedMemory > -1);
         }
@@ -689,7 +691,7 @@
                         }
                         @Override
                         public long getTotalCapacity() {
-                            return Bits.usedMemory;
+                            return Bits.totalCapacity;
                         }
                         @Override
                         public long getMemoryUsed() {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/nio/Buffer/LimitDirectMemory.java	Fri Oct 15 15:09:37 2010 +0100
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * 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.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.nio.ByteBuffer;
+import java.util.Properties;
+
+public class LimitDirectMemory {
+    private static int K = 1024;
+
+    public static void main(String [] args) throws Exception {
+        if (args.length < 2)
+            throw new RuntimeException();
+        boolean throwp = parseThrow(args[0]);
+        int size = parseSize(args[1]);
+        int incr = (args.length > 2 ? parseSize(args[2]) : size);
+
+        Properties p = System.getProperties();
+        if (p.getProperty("sun.nio.MaxDirectMemorySize") != null)
+            throw new RuntimeException("sun.nio.MaxDirectMemorySize defined");
+
+        ByteBuffer [] b = new ByteBuffer[K];
+
+        // Fill up most/all of the direct memory
+        int i = 0;
+        while (size >= incr) {
+            b[i++] = ByteBuffer.allocateDirect(incr);
+            size -= incr;
+        }
+
+        if (throwp) {
+            try {
+                b[i] = ByteBuffer.allocateDirect(incr);
+                throw new RuntimeException("OutOfMemoryError not thrown: "
+                                           + incr);
+            } catch (OutOfMemoryError e) {
+                e.printStackTrace(System.out);
+                System.out.println("OK - Error thrown as expected ");
+            }
+        } else {
+            b[i] = ByteBuffer.allocateDirect(incr);
+            System.out.println("OK - Error not thrown");
+        }
+    }
+
+    private static boolean parseThrow(String s) {
+        if (s.equals("true"))  return true;
+        if (s.equals("false")) return false;
+        throw new RuntimeException("Unrecognized expectation: " + s);
+    }
+
+    private static int parseSize(String size) throws Exception {
+
+        if (size.equals("DEFAULT"))
+            return (int)Runtime.getRuntime().maxMemory();
+        if (size.equals("DEFAULT+1"))
+            return (int)Runtime.getRuntime().maxMemory() + 1;
+        if (size.equals("DEFAULT+1M"))
+            return (int)Runtime.getRuntime().maxMemory() + (1 << 20);
+        if (size.equals("DEFAULT-1"))
+            return (int)Runtime.getRuntime().maxMemory() - 1;
+        if (size.equals("DEFAULT/2"))
+            return (int)Runtime.getRuntime().maxMemory() / 2;
+
+        int idx = 0, len = size.length();
+
+        int result = 1;
+        for (int i = 0; i < len; i++) {
+            if (Character.isDigit(size.charAt(i))) idx++;
+            else break;
+        }
+
+        if (idx == 0)
+            throw new RuntimeException("No digits detected: " + size);
+
+        result = Integer.parseInt(size.substring(0, idx));
+
+        if (idx < len) {
+            for (int i = idx; i < len; i++) {
+                switch(size.charAt(i)) {
+                case 'T': case 't': result *= K; // fall through
+                case 'G': case 'g': result *= K; // fall through
+                case 'M': case 'm': result *= K; // fall through
+                case 'K': case 'k': result *= K;
+                    break;
+                default:
+                    throw new RuntimeException("Unrecognized size: " + size);
+                }
+            }
+        }
+        return result;
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/nio/Buffer/LimitDirectMemory.sh	Fri Oct 15 15:09:37 2010 +0100
@@ -0,0 +1,99 @@
+#!/bin/sh
+
+#
+# Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
+# DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+#
+# This code is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License version 2 only, as
+# 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.
+#
+# Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+# or visit www.oracle.com if you need additional information or have any
+# questions.
+#
+
+# @test
+# @bug 4627316 6743526
+# @summary Test option to limit direct memory allocation
+#
+# @build LimitDirectMemory
+# @run shell LimitDirectMemory.sh
+
+# set platform-dependent variable
+OS=`uname -s`
+case "$OS" in
+  SunOS | Linux ) TMP=/tmp ;;
+  Windows* ) TMP="c:/temp" ;;
+  * )
+    echo "Unrecognized system!"
+    exit 1;
+    ;;
+esac
+
+TMP1=${TMP}/tmp1_$$
+
+runTest() {
+  echo "Testing: $*"
+  ${TESTJAVA}/bin/java $*
+  if [ $? -eq 0 ]
+  then echo "--- passed as expected"
+  else
+    echo "--- failed"
+    exit 1
+  fi
+}
+
+launchFail() {
+  echo "Testing: -XX:MaxDirectMemorySize=$* -cp ${TESTCLASSES} \
+     LimitDirectMemory true DEFAULT DEFAULT+1M"
+  ${TESTJAVA}/bin/java -XX:MaxDirectMemorySize=$* -cp ${TESTCLASSES} \
+     LimitDirectMemory true DEFAULT DEFAULT+1M > ${TMP1} 2>&1
+  cat ${TMP1}
+  cat ${TMP1} | grep -s "Unrecognized VM option: \'MaxDirectMemorySize="
+  if [ $? -ne 0 ]
+    then echo "--- failed as expected"
+  else
+    echo "--- failed"
+    exit 1
+  fi
+}
+
+# $java LimitDirectMemory throwp fill_direct_memory size_per_buffer
+
+# Memory is properly limited using multiple buffers.
+runTest -XX:MaxDirectMemorySize=10 -cp ${TESTCLASSES} LimitDirectMemory true 10 1
+runTest -XX:MaxDirectMemorySize=1k -cp ${TESTCLASSES} LimitDirectMemory true 1k 100
+runTest -XX:MaxDirectMemorySize=10m -cp ${TESTCLASSES} LimitDirectMemory true 10m 10m
+
+# We can increase the amount of available memory.
+runTest -XX:MaxDirectMemorySize=65M -cp ${TESTCLASSES} \
+  LimitDirectMemory false 64M 65M
+
+# Exactly the default amount of memory is available.
+runTest -cp ${TESTCLASSES} LimitDirectMemory false 10 1
+runTest -cp ${TESTCLASSES} LimitDirectMemory false 0 DEFAULT
+runTest -cp ${TESTCLASSES} LimitDirectMemory true 0 DEFAULT+1
+
+# We should be able to eliminate direct memory allocation entirely.
+runTest -XX:MaxDirectMemorySize=0 -cp ${TESTCLASSES} LimitDirectMemory true 0 1
+
+# Setting the system property should not work so we should be able to allocate
+# the default amount.
+runTest -Dsun.nio.MaxDirectMemorySize=1K -cp ${TESTCLASSES} \
+  LimitDirectMemory false DEFAULT-1 DEFAULT/2
+
+# Various bad values fail to launch the VM.
+launchFail foo
+launchFail 10kmt
+launchFail -1