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   * "License"); you may not use this file except in compliance
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   *
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  package org.apache.cassandra.test.microbench;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.nio.file.Files;
  import java.util.UUID;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.cassandra.io.util.File;
  import org.apache.cassandra.io.util.FileUtils;
  import org.apache.cassandra.utils.DirectorySizeCalculator;
  import org.openjdk.jmh.annotations.*;
  import org.openjdk.jmh.infra.Blackhole;
  
  @BenchmarkMode(Mode.AverageTime)
  @OutputTimeUnit(TimeUnit.MILLISECONDS)
  @Warmup(iterations = 1)
  @Measurement(iterations = 30)
  @Fork(value = 1, jvmArgsAppend = "-Xmx512M")
  @Threads(1)
  @State(Scope.Benchmark)
  public class DirectorySizerBench
  {
      private File tempDir;
      private DirectorySizeCalculator sizer;
  
      @Setup(Level.Trial)
      public void setUp() throws IOException
      {
          tempDir = new File(Files.createTempDirectory(randString()));
  
          // Since #'s on laptops and commodity desktops are so useful in considering enterprise virtualized server environments...
  
          // Spinning disk 7200rpm 1TB, win10, ntfs, i6600 skylake, 256 files:
          // [java] Result: 0.581 ▒(99.9%) 0.003 ms/op [Average]
          // [java]   Statistics: (min, avg, max) = (0.577, 0.581, 0.599), stdev = 0.005
          // [java]   Confidence interval (99.9%): [0.577, 0.584]
  
          // Same hardware, 25600 files:
          // [java] Result: 56.990 ▒(99.9%) 0.374 ms/op [Average]
          // [java]   Statistics: (min, avg, max) = (56.631, 56.990, 59.829), stdev = 0.560
          // [java]   Confidence interval (99.9%): [56.616, 57.364]
  
          // #'s on a rmbp, 2014, SSD, ubuntu 15.10, ext4, i7-4850HQ @ 2.3, 25600 samples
          // [java] Result: 74.714 ±(99.9%) 0.558 ms/op [Average]
          // [java]   Statistics: (min, avg, max) = (73.687, 74.714, 76.872), stdev = 0.835
          // [java]   Confidence interval (99.9%): [74.156, 75.272]
  
          // Test w/25,600 files, 100x the load of a full default CommitLog (8192) divided by size (32 per)
          populateRandomFiles(tempDir, 25600);
          sizer = new DirectorySizeCalculator();
      }
  
      @TearDown
      public void tearDown()
      {
          FileUtils.deleteRecursive(tempDir);
      }
  
      private void populateRandomFiles(File dir, int count) throws IOException
      {
          for (int i = 0; i < count; i++)
          {
              PrintWriter pw = new PrintWriter(dir + File.pathSeparator() + randString(), "UTF-8");
              pw.write(randString());
              pw.close();
          }
      }
  
      private String randString()
      {
          return UUID.randomUUID().toString();
      }
  
      @Benchmark
      public void countFiles(final Blackhole bh) throws IOException
      {
          Files.walkFileTree(tempDir.toPath(), sizer);
      }
  }
  