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diff --git a/vespajlib/developernotes/CopyOnWriteHashMapBenchmark.java b/vespajlib/developernotes/CopyOnWriteHashMapBenchmark.java
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+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.concurrent;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author <a href="mailto:balder@yahoo-inc.com">Henning Baldersheim</a>
+ * @since 5.2
+ */
+public class RcuHashMapBenchmark {
+    static class Actor implements Runnable {
+        private final CopyOnWriteHashMap<Long, Long> m;
+        private long mSum = 0;
+        private long mMissRate = 0;
+        Actor(CopyOnWriteHashMap<Long, Long> m) {
+            this.m = m;
+        }
+        @Override
+        public void run() {
+            final int NUM_UPDATES=100;
+            final long NUM_LOOKUPS=10000000;
+            final List<Long> upd = new ArrayList<Long>(NUM_UPDATES);
+            upd.add(0l);
+            long missRate = 0;
+            long sum = 0;
+            for (long i=0; i < NUM_LOOKUPS; i++) {
+                long t = i%upd.size();
+                Long v = m.get(upd.get((int)t));
+                if (v == null) {
+                    missRate++;
+                    m.put(upd.get((int)t), i);
+                    sum += i;
+                } else {
+                    sum += v;
+                }
+                if (i%(NUM_LOOKUPS/NUM_UPDATES) == 0) {
+                    upd.add((long)upd.size());
+                }
+            }
+            synchronized (this) {
+                mSum = sum;
+                mMissRate = missRate;
+            }
+        }
+        long getSum() { synchronized (this) { return mSum; } }
+        long getMissRate() { synchronized (this) { return mMissRate;} }
+    }
+    RcuHashMapBenchmark(int numThreads) {
+        CopyOnWriteHashMap<Long, Long> m = new CopyOnWriteHashMap<Long, Long>();
+        Thread[] threads = new Thread[numThreads];
+        Actor [] actors = new Actor[threads.length];
+        for (int i = 0; i < threads.length; ++i) {
+            Actor a = new Actor(m);
+            actors[i] = a;
+            threads[i] = new Thread(a);
+        }
+        runAll(threads);
+        long missRate=0;
+        long sum=0;
+        for (Actor a : actors) {
+            missRate += a.getMissRate();
+            sum += a.getSum();
+            System.out.println("Missrate: " + a.getMissRate() + " sum = " + a.getSum());
+        }
+        System.out.println("Total Missrate: " + missRate + " sum = " + sum);
+    }
+
+    private void runAll(Thread[] threads) {
+        for (Thread t : threads) {
+            t.start();
+        }
+        for (Thread t : threads) {
+            try {
+                t.join();
+            } catch (InterruptedException e) {
+                // nop
+            }
+        }
+    }
+    public static void main(String[] args) {
+        long start, end;
+        start = System.currentTimeMillis();
+        new RcuHashMapBenchmark(1);
+        end = System.currentTimeMillis();
+        System.out.println("Elapsed during warmup: " + (end - start) + " ms.");
+        for (int i=0; i < 16; i++) {
+            start = System.currentTimeMillis();
+            new RcuHashMapBenchmark(i+1);
+            end = System.currentTimeMillis();
+            System.out.println("Elapsed during " + (i+1) + " threads: " + (end - start) + " ms.");
+        }
+
+    }
+}