--- old/src/share/classes/java/lang/ref/Reference.java 2014-02-20 17:46:35.977637977 +0100 +++ new/src/share/classes/java/lang/ref/Reference.java 2014-02-20 17:46:35.879639705 +0100 @@ -26,6 +26,8 @@ package java.lang.ref; import sun.misc.Cleaner; +import sun.misc.JavaLangRefAccess; +import sun.misc.SharedSecrets; /** * Abstract base class for reference objects. This class defines the @@ -147,49 +149,73 @@ } public void run() { - for (;;) { - Reference r; - Cleaner c; - try { - synchronized (lock) { - if (pending != null) { - r = pending; - // 'instanceof' might throw OutOfMemoryError sometimes - // so do this before un-linking 'r' from the 'pending' chain... - c = r instanceof Cleaner ? (Cleaner) r : null; - // unlink 'r' from 'pending' chain - pending = r.discovered; - r.discovered = null; - } else { - // The waiting on the lock may cause an OutOfMemoryError - // because it may try to allocate exception objects. - lock.wait(); - continue; - } - } - } catch (OutOfMemoryError x) { - // Give other threads CPU time so they hopefully drop some live references - // and GC reclaims some space. - // Also prevent CPU intensive spinning in case 'r instanceof Cleaner' above - // persistently throws OOME for some time... - Thread.yield(); - // retry - continue; - } catch (InterruptedException x) { - // retry - continue; - } + while (true) { + tryHandlePending(true); + } + } + } - // Fast path for cleaners - if (c != null) { - c.clean(); - continue; + /** + * Try handle pending {@link Reference} if there is one.

+ * Return {@code true} as a hint that there might be another + * {@link Reference} pending or {@code false} when there are no more pending + * {@link Reference}s at the moment and the program can do some other + * useful work instead of looping. + * + * @param waitForNotify if {@code true} and there was no pending + * {@link Reference}, wait until notified from VM + * or interrupted; if {@code false}, return immediately + * when there is no pending {@link Reference}. + * @return {@code true} if there was a {@link Reference} pending and it + * was processed, or we waited for notification and either got it + * or thread was interrupted before being notified; + * {@code false} otherwise. + */ + static boolean tryHandlePending(boolean waitForNotify) { + Reference r; + Cleaner c; + try { + synchronized (lock) { + if (pending != null) { + r = pending; + // 'instanceof' might throw OutOfMemoryError sometimes + // so do this before un-linking 'r' from the 'pending' chain... + c = r instanceof Cleaner ? (Cleaner) r : null; + // unlink 'r' from 'pending' chain + pending = r.discovered; + r.discovered = null; + } else { + // The waiting on the lock may cause an OutOfMemoryError + // because it may try to allocate exception objects. + if (waitForNotify) { + lock.wait(); + } + // retry if waited + return waitForNotify; } - - ReferenceQueue q = r.queue; - if (q != ReferenceQueue.NULL) q.enqueue(r); } + } catch (OutOfMemoryError x) { + // Give other threads CPU time so they hopefully drop some live references + // and GC reclaims some space. + // Also prevent CPU intensive spinning in case 'r instanceof Cleaner' above + // persistently throws OOME for some time... + Thread.yield(); + // retry + return true; + } catch (InterruptedException x) { + // retry + return true; } + + // Fast path for cleaners + if (c != null) { + c.clean(); + return true; + } + + ReferenceQueue q = r.queue; + if (q != ReferenceQueue.NULL) q.enqueue(r); + return true; } static { @@ -204,8 +230,15 @@ handler.setPriority(Thread.MAX_PRIORITY); handler.setDaemon(true); handler.start(); - } + // provide access in SharedSecrets + SharedSecrets.setJavaLangRefAccess(new JavaLangRefAccess() { + @Override + public boolean tryHandlePendingReference() { + return tryHandlePending(false); + } + }); + } /* -- Referent accessor and setters -- */ --- old/src/share/classes/java/nio/Bits.java 2014-02-20 17:46:36.211633850 +0100 +++ new/src/share/classes/java/nio/Bits.java 2014-02-20 17:46:36.115635543 +0100 @@ -26,6 +26,11 @@ package java.nio; import java.security.AccessController; +import java.util.concurrent.atomic.AtomicLong; +import java.util.concurrent.atomic.LongAdder; + +import sun.misc.JavaLangRefAccess; +import sun.misc.SharedSecrets; import sun.misc.Unsafe; import sun.misc.VM; @@ -621,55 +626,103 @@ // direct buffer memory. This value may be changed during VM // initialization if it is launched with "-XX:MaxDirectMemorySize=". private static volatile long maxMemory = VM.maxDirectMemory(); - private static volatile long reservedMemory; - private static volatile long totalCapacity; - private static volatile long count; - private static boolean memoryLimitSet = false; + private static final AtomicLong reservedMemory = new AtomicLong(); + private static final AtomicLong totalCapacity = new AtomicLong(); + private static final AtomicLong count = new AtomicLong(); + private static volatile boolean memoryLimitSet = false; + // max. number of sleeps during try-reserving with exponentially + // increasing delay before throwing OutOfMemoryError: + // 1, 2, 4, 8, 16, 32, 64, 128, 256 (total 511 ms ~ 0.5 s) + // which means that OOME will be thrown after 0.5 s of trying + private static final int MAX_SLEEPS = 9; // These methods should be called whenever direct memory is allocated or // 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; - } - // -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; - totalCapacity += cap; - count++; + + if (!memoryLimitSet && VM.isBooted()) { + maxMemory = VM.maxDirectMemory(); + memoryLimitSet = true; + } + + // optimist! + if (tryReserveMemory(size, cap)) { + return; + } + + final JavaLangRefAccess jlra = SharedSecrets.getJavaLangRefAccess(); + + // retry while helping enqueue pending Reference objects + // which includes executing pending Cleaner(s) which includes + // Cleaner(s) that free direct buffer memory + while (jlra.tryHandlePendingReference()) { + if (tryReserveMemory(size, cap)) { return; } } + // trigger VM's Reference processing System.gc(); + + // a retry loop with exponential back-off delays + // (this gives VM some time to do it's job) + boolean interrupted = false; try { - Thread.sleep(100); - } catch (InterruptedException x) { - // Restore interrupt status - Thread.currentThread().interrupt(); + long sleepTime = 1; + int sleeps = 0; + while (true) { + if (tryReserveMemory(size, cap)) { + return; + } + if (sleeps >= MAX_SLEEPS) { + break; + } + if (!jlra.tryHandlePendingReference()) { + try { + Thread.sleep(sleepTime); + sleepTime <<= 1; + sleeps++; + } catch (InterruptedException e) { + interrupted = true; + } + } + } + + // no luck + throw new OutOfMemoryError("Direct buffer memory"); + + } finally { + if (interrupted) { + // don't swallow interrupts + Thread.currentThread().interrupt(); + } } - synchronized (Bits.class) { - if (totalCapacity + cap > maxMemory) - throw new OutOfMemoryError("Direct buffer memory"); - reservedMemory += size; - totalCapacity += cap; - count++; + } + + private static boolean tryReserveMemory(long size, int cap) { + + // -XX:MaxDirectMemorySize limits the total capacity rather than the + // actual memory usage, which will differ when buffers are page + // aligned. + long totalCap; + while (cap <= maxMemory - (totalCap = totalCapacity.get())) { + if (totalCapacity.compareAndSet(totalCap, totalCap + cap)) { + reservedMemory.addAndGet(size); + count.incrementAndGet(); + return true; + } } + return false; } - static synchronized void unreserveMemory(long size, int cap) { - if (reservedMemory > 0) { - reservedMemory -= size; - totalCapacity -= cap; - count--; - assert (reservedMemory > -1); - } + + static void unreserveMemory(long size, int cap) { + long cnt = count.decrementAndGet(); + long reservedMem = reservedMemory.addAndGet(-size); + long totalCap = totalCapacity.addAndGet(-cap); + assert cnt >= 0 && reservedMem >= 0 && totalCap >= 0; } // -- Monitoring of direct buffer usage -- @@ -687,15 +740,15 @@ } @Override public long getCount() { - return Bits.count; + return Bits.count.get(); } @Override public long getTotalCapacity() { - return Bits.totalCapacity; + return Bits.totalCapacity.get(); } @Override public long getMemoryUsed() { - return Bits.reservedMemory; + return Bits.reservedMemory.get(); } }; } --- old/src/share/classes/sun/misc/SharedSecrets.java 2014-02-20 17:46:36.450629636 +0100 +++ new/src/share/classes/sun/misc/SharedSecrets.java 2014-02-20 17:46:36.352631364 +0100 @@ -45,6 +45,7 @@ private static final Unsafe unsafe = Unsafe.getUnsafe(); private static JavaUtilJarAccess javaUtilJarAccess; private static JavaLangAccess javaLangAccess; + private static JavaLangRefAccess javaLangRefAccess; private static JavaIOAccess javaIOAccess; private static JavaNetAccess javaNetAccess; private static JavaNetHttpCookieAccess javaNetHttpCookieAccess; @@ -76,6 +77,14 @@ return javaLangAccess; } + public static void setJavaLangRefAccess(JavaLangRefAccess jlra) { + javaLangRefAccess = jlra; + } + + public static JavaLangRefAccess getJavaLangRefAccess() { + return javaLangRefAccess; + } + public static void setJavaNetAccess(JavaNetAccess jna) { javaNetAccess = jna; } --- /dev/null 2014-02-20 08:25:21.320449846 +0100 +++ new/src/share/classes/sun/misc/JavaLangRefAccess.java 2014-02-20 17:46:36.581627326 +0100 @@ -0,0 +1,39 @@ +/* + * Copyright (c) 2014, 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. Oracle designates this + * particular file as subject to the "Classpath" exception as provided + * by Oracle in the LICENSE file that accompanied this code. + * + * 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 sun.misc; + +public interface JavaLangRefAccess { + + /** + * Help ReferenceHandler thread process next pending + * {@link java.lang.ref.Reference} + * + * @return {@code true} if there was a pending reference and it + * was enqueue-ed or {@code false} if there was no + * pending reference + */ + boolean tryHandlePendingReference(); +} --- /dev/null 2014-02-20 08:25:21.320449846 +0100 +++ new/test/java/nio/Buffer/DirectBufferAllocTest.java 2014-02-20 17:46:36.808623323 +0100 @@ -0,0 +1,174 @@ +/* + * Copyright (c) 2014, 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 6857566 + * @summary DirectByteBuffer garbage creation can outpace reclamation + * + * @run main/othervm -XX:MaxDirectMemorySize=128m DirectBufferAllocTest + */ + +import java.nio.ByteBuffer; +import java.util.List; +import java.util.concurrent.*; +import java.util.stream.Collectors; +import java.util.stream.IntStream; + +public class DirectBufferAllocTest { + // defaults + static final int RUN_TIME_SECONDS = 5; + static final int MIN_THREADS = 4; + static final int MAX_THREADS = 64; + static final int CAPACITY = 1024 * 1024; // bytes + + /** + * This test spawns multiple threads that constantly allocate direct + * {@link ByteBuffer}s in a loop, trying to provoke {@link OutOfMemoryError}.

+ * When run without command-line arguments, it runs as a regression test + * for at most 5 seconds.

+ * Command line arguments: + * 

+     * -r run-time-seconds (duration of successful test - default 5 s)
+     * -t threads (default is 2 * # of CPUs, at least 4 but no more than 64)
+     * -c capacity (of direct buffers in bytes - default is 1MB)
+     * -p print-alloc-time-batch-size (every "batch size" iterations,
+     *                                 average time per allocation is printed)
+     *
+ * Use something like the following to run a 10 minute stress test and + * print allocation times as it goes: + * 
+     * java -XX:MaxDirectMemorySize=128m DirectBufferAllocTest -r 600 -t 32 -p 5000
+     *
+ */ + public static void main(String[] args) throws Exception { + int runTimeSeconds = RUN_TIME_SECONDS; + int threads = Math.max( + Math.min( + Runtime.getRuntime().availableProcessors() * 2, + MAX_THREADS + ), + MIN_THREADS + ); + int capacity = CAPACITY; + int printBatchSize = 0; + + // override with command line arguments + for (int i = 0; i < args.length; i++) { + switch (args[i]) { + case "-r": + runTimeSeconds = Integer.parseInt(args[++i]); + break; + case "-t": + threads = Integer.parseInt(args[++i]); + break; + case "-c": + capacity = Integer.parseInt(args[++i]); + break; + case "-p": + printBatchSize = Integer.parseInt(args[++i]); + break; + default: + System.err.println( + "Usage: java" + + " [-XX:MaxDirectMemorySize=XXXm]" + + " DirectBufferAllocTest" + + " [-r run-time-seconds]" + + " [-t threads]" + + " [-c capacity-of-direct-buffers]" + + " [-p print-alloc-time-batch-size]" + ); + System.exit(-1); + } + } + + System.out.printf( + "Allocating direct ByteBuffers with capacity %d bytes, using %d threads for %d seconds...\n", + capacity, threads, runTimeSeconds + ); + + ExecutorService executor = Executors.newFixedThreadPool(threads); + + int pbs = printBatchSize; + int cap = capacity; + + List> futures = + IntStream.range(0, threads) + .mapToObj( + i -> (Callable) () -> { + long t0 = System.nanoTime(); + loop: + while (true) { + for (int n = 0; pbs == 0 || n < pbs; n++) { + if (Thread.interrupted()) { + break loop; + } + ByteBuffer.allocateDirect(cap); + } + long t1 = System.nanoTime(); + if (pbs > 0) { + System.out.printf( + "Thread %2d: %5.2f ms/allocation\n", + i, ((double) (t1 - t0) / (1_000_000d * pbs)) + ); + } + t0 = t1; + } + return null; + } + ) + .map(executor::submit) + .collect(Collectors.toList()); + + for (int i = 0; i < runTimeSeconds; i++) { + if (futures.stream().anyMatch(Future::isDone)) { + break; + } + Thread.sleep(1000L); + } + + Exception exception = null; + for (Future future : futures) { + if (future.isDone()) { + try { + future.get(); + } catch (ExecutionException e) { + if (exception == null) { + exception = new RuntimeException("Errors encountered!"); + } + exception.addSuppressed(e.getCause()); + } + } else { + future.cancel(true); + } + } + + executor.shutdown(); + + if (exception != null) { + throw exception; + } else { + System.out.printf("No errors after %d seconds.\n", runTimeSeconds); + } + } +}