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   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
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   * See the License for the specific language governing permissions and
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  package org.apache.cassandra.test.microbench;
  
  import java.util.concurrent.TimeUnit;
  
  import io.netty.util.concurrent.FastThreadLocal;
  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.Threads;
  import org.openjdk.jmh.annotations.Warmup;
  import org.openjdk.jmh.infra.Blackhole;
  
  @BenchmarkMode(Mode.AverageTime)
  @OutputTimeUnit(TimeUnit.NANOSECONDS)
  @Warmup(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
  @Measurement(iterations = 5, time = 2, timeUnit = TimeUnit.SECONDS)
  @Fork(value = 1, jvmArgsAppend = {"-Xmx512M", "-Djmh.executor=CUSTOM", "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor"})
  @Threads(4) // make sure this matches the number of _physical_cores_
  @State(Scope.Benchmark)
  public class FastThreadLocalBench
  {
      @Param({"2", "4", "8", "12"})
      private int variables = 2;
  
      static final int max = 20;
      static final ThreadLocal[] threadLocals = new ThreadLocal[max];
      static final FastThreadLocal[] fastThreadLocals = new FastThreadLocal[max];
      static
      {
          for (int i = 0; i < max; i++)
          {
              threadLocals[i] = ThreadLocal.withInitial(Object::new);
              fastThreadLocals[i] = new FastThreadLocal() {
                  protected Object initialValue() throws Exception
                  {
                      return new Object();
                  }
              };
          }
      }
  
      @State(Scope.Thread)
      public static class FastThreadLocalBenchState
      {
          public int index;
      }
  
      @Benchmark
      public void baseline(FastThreadLocalBenchState state, Blackhole bh)
      {
          if (variables != 2)
              throw new IllegalArgumentException("skipped");
  
          bh.consume("foo");
      }
  
      @Benchmark
      public void threadLocal(FastThreadLocalBenchState state, Blackhole bh)
      {
          bh.consume(threadLocals[state.index % max].get());
      }
  
      @Benchmark
      public void fastThreadLocal(FastThreadLocalBenchState state, Blackhole bh)
      {
          bh.consume(fastThreadLocals[state.index % max].get());
      }
  }
  