Issue #6974 - add LogArrayByteBufferPool that does exponential scalin…

…g of bucket size.

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-io/src/main/java/org/eclipse/jetty/io/LogArrayByteBufferPool.java

@@ -0,0 +1,118 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2021 Mort Bay Consulting Pty Ltd and others.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.io;
+
+/**
+ * Extension of the {@link ArrayByteBufferPool} whose bucket sizes increase exponentially instead of linearly.
+ * Each bucket will be double the size of the previous bucket, this decreases the amounts of buckets required
+ * which can lower total memory usage if buffers are often being acquired of different sizes. However as there are
+ * fewer buckets this will also increase the contention on each bucket.
+ */
+public class LogArrayByteBufferPool extends ArrayByteBufferPool
+{
+    /**
+     * Creates a new ByteBufferPool with a default configuration.
+     */
+    public LogArrayByteBufferPool()
+    {
+        this(-1, -1, -1);
+    }
+
+    /**
+     * Creates a new ByteBufferPool with the given configuration.
+     *
+     * @param minCapacity the minimum ByteBuffer capacity
+     * @param maxCapacity the maximum ByteBuffer capacity
+     */
+    public LogArrayByteBufferPool(int minCapacity, int maxCapacity)
+    {
+        this(minCapacity, maxCapacity, -1, -1, -1);
+    }
+
+    /**
+     * Creates a new ByteBufferPool with the given configuration.
+     *
+     * @param minCapacity the minimum ByteBuffer capacity
+     * @param maxCapacity the maximum ByteBuffer capacity
+     * @param maxQueueLength the maximum ByteBuffer queue length
+     */
+    public LogArrayByteBufferPool(int minCapacity, int maxCapacity, int maxQueueLength)
+    {
+        this(minCapacity, maxCapacity, maxQueueLength, -1, -1);
+    }
+
+    /**
+     * Creates a new ByteBufferPool with the given configuration.
+     *
+     * @param minCapacity the minimum ByteBuffer capacity
+     * @param maxCapacity the maximum ByteBuffer capacity
+     * @param maxQueueLength the maximum ByteBuffer queue length
+     * @param maxHeapMemory the max heap memory in bytes
+     * @param maxDirectMemory the max direct memory in bytes
+     */
+    public LogArrayByteBufferPool(int minCapacity, int maxCapacity, int maxQueueLength, long maxHeapMemory, long maxDirectMemory)
+    {
+        super(minCapacity, 1, maxCapacity, maxQueueLength, maxHeapMemory, maxDirectMemory);
+    }
+
+    @Override
+    protected int getBucketNumber(int capacity)
+    {
+        return 32 - Integer.numberOfLeadingZeros(capacity - 1);
+    }
+
+    @Override
+    protected int getBucketCapacity(int bucket)
+    {
+        return 1 << bucket;
+    }
+
+    @Override
+    protected void releaseMemory(boolean direct)
+    {
+        long oldest = Long.MAX_VALUE;
+        int index = -1;
+        Bucket[] buckets = bucketsFor(direct);
+        for (int i = 0; i < buckets.length; ++i)
+        {
+            Bucket bucket = buckets[i];
+            if (bucket == null || bucket.isEmpty())
+                continue;
+            long lastUpdate = bucket.getLastUpdate();
+            if (lastUpdate < oldest)
+            {
+                oldest = lastUpdate;
+                index = i;
+            }
+        }
+        if (index >= 0)
+        {
+            Bucket bucket = buckets[index];
+
+            // The same bucket may be concurrently
+            // removed, so we need this null guard.
+            if (bucket != null)
+            {
+                // Acquire a buffer but never return it to the pool.
+                bucket.acquire();
+                bucket.resetUpdateTime();
+            }
+        }
+    }
+}

tests/test-integration/src/test/java/org/eclipse/jetty/test/WebSocketMemoryTest.java

@@ -10,7 +10,7 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-import org.eclipse.jetty.io.MappedByteBufferPool;
+import org.eclipse.jetty.io.LogArrayByteBufferPool;
 import org.eclipse.jetty.jmx.MBeanContainer;
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.ServerConnector;
@@ -57,10 +57,10 @@ public void before() throws Exception
     {
         _server = new Server();
 //        _server.addBean(new LogArrayByteBufferPool(512, -1, -1, maxMemory, maxMemory));
-        int maxMemory = 0;//-1;//1024 * 8;
+        int maxMemory = 1024 * 1024 * 64;
 //        ByteBufferPool bufferPool = new ArrayByteBufferPool(-1, -1, -1, -1, maxMemory, maxMemory);
-//        ByteBufferPool bufferPool = new LogArrayByteBufferPool(-1, -1, -1, maxMemory, maxMemory);
-        MappedByteBufferPool bufferPool = new MappedByteBufferPool(-1, -1, null, maxMemory, maxMemory);
+        LogArrayByteBufferPool bufferPool = new LogArrayByteBufferPool(-1, 1024 * 1024, -1, maxMemory, maxMemory);
+//        MappedByteBufferPool bufferPool = new MappedByteBufferPool(-1, -1, null, maxMemory, maxMemory);
         bufferPool.setDetailedDump(true);
 //        ByteBufferPool bufferPool = new NullByteBufferPool();
         _server.addBean(bufferPool);