8357959: (bf) ByteBuffer.allocateDirect initialization can result in large TTSP spikes

src/java.base/share/classes/java/nio/Bits.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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
@@ -234,4 +234,28 @@ public long getMemoryUsed() {
     // of an element by element copy.  These numbers may change over time.
     static final int JNI_COPY_TO_ARRAY_THRESHOLD   = 6;
     static final int JNI_COPY_FROM_ARRAY_THRESHOLD = 6;
+
+    // Maximum number of bytes to set in one call to {@code Unsafe.setMemory}.
+    // This threshold allows safepoint polling during large memory operations.
+    static final long UNSAFE_SET_THRESHOLD = 1024 * 1024;
+
+    /**
+     * Sets a block of memory starting from a given address to a specified byte value.
+     *
+     * @param srcAddr
+     *        the starting memory address
+     * @param count
+     *        the number of bytes to set
+     * @param value
+     *        the byte value to set
+     */
+    static void setMemory(long srcAddr, long count, byte value) {
+        long offset = 0;
+        while (offset < count) {
+            long len = Math.min(UNSAFE_SET_THRESHOLD, count - offset);
+            UNSAFE.setMemory(srcAddr + offset, len, value);
+            offset += len;
+        }
+    }
+
 }

src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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
@@ -117,7 +117,7 @@ class Direct$Type$Buffer$RW$$BO$
             Bits.unreserveMemory(size, cap);
             throw x;
         }
-        UNSAFE.setMemory(base, size, (byte) 0);
+        Bits.setMemory(base, size, (byte) 0);
         if (pa && (base % ps != 0)) {
             // Round up to page boundary
             address = base + ps - (base & (ps - 1));

test/jdk/java/nio/Buffer/AllocateDirectInit.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2007, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2025, 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
@@ -23,29 +23,60 @@
 
 /**
  * @test
- * @bug 4490253 6535542
+ * @bug 4490253 6535542 8357959
+ * @key randomness
+ * @library /test/lib
+ * @build jdk.test.lib.RandomFactory
  * @summary Verify that newly allocated direct buffers are initialized.
+ * @run main/othervm AllocateDirectInit
  */
 
 import java.nio.ByteBuffer;
+import java.util.Random;
+
+import jdk.test.lib.RandomFactory;
 
 public class AllocateDirectInit {
+    private static final int MAX_BIN_LIMIT = 16 * 1024 * 1024;
+    private static final int MAX_DEC_LIMIT = 10 * 1000 * 1000;
+    private static final int TRIES_PER_LIMIT = 1024;
+
+    private static final Random RND = RandomFactory.getRandom();
+
     public static void main(String [] args){
-        for (int i = 0; i < 1024; i++) {
-            ByteBuffer bb = ByteBuffer.allocateDirect(1024);
-//          printByteBuffer(bb);
-            for (bb.position(0); bb.position() < bb.limit(); ) {
-                if ((bb.get() & 0xff) != 0)
-                    throw new RuntimeException("uninitialized buffer, position = "
-                                               + bb.position());
+        // Try power of two limits
+        for (int limit = 1; limit < MAX_BIN_LIMIT; limit *= 2) {
+            check(ByteBuffer.allocateDirect(limit - 1));
+            check(ByteBuffer.allocateDirect(limit));
+            check(ByteBuffer.allocateDirect(limit + 1));
+        }
+
+        // Try power of ten limits
+        for (int limit = 1; limit < MAX_DEC_LIMIT; limit *= 10) {
+            check(ByteBuffer.allocateDirect(limit - 1));
+            check(ByteBuffer.allocateDirect(limit));
+            check(ByteBuffer.allocateDirect(limit + 1));
+        }
+
+        // Try random sizes within power of two limits
+        for (int limit = 1; limit < MAX_BIN_LIMIT; limit *= 2) {
+            for (int t = 0; t < TRIES_PER_LIMIT; t++) {
+                check(ByteBuffer.allocateDirect(RND.nextInt(limit)));
             }
         }
     }
 
-    private static void printByteBuffer(ByteBuffer bb) {
-        System.out.print("byte [");
-        for (bb.position(0); bb.position() < bb.limit(); )
-            System.out.print(" " + Integer.toHexString(bb.get() & 0xff));
-        System.out.println(" ]");
+    private static void check(ByteBuffer bb) {
+        while (bb.hasRemaining()) {
+            if (bb.get() != 0) {
+                int mismatchPos = bb.position();
+                System.out.print("byte [");
+                for (bb.position(0); bb.position() < bb.limit(); ) {
+                    System.out.print(" " + Integer.toHexString(bb.get() & 0xff));
+                }
+                System.out.println(" ]");
+                throw new RuntimeException("uninitialized buffer, position = " + mismatchPos);
+            }
+        }
     }
 }

test/micro/org/openjdk/bench/java/nio/DirectByteBufferAlloc.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright Amazon.com Inc. 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.
+ *
+ */
+package org.openjdk.bench.java.nio;
+
+
+import java.nio.ByteBuffer;
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Thread)
+@Warmup(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
+@Measurement(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
+@Fork(3)
+public class DirectByteBufferAlloc {
+
+    @Param({
+            "128", // 128 bytes
+            "1024", // 1KB
+            "1048576", // 1 MB
+            "16777216" // 16MB
+    })
+    public int bytes;
+
+    @Benchmark
+    public ByteBuffer allocateDirectBuffer() {
+        return ByteBuffer.allocateDirect(bytes);
+    }
+}