text: // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file. See the AUTHORS file for names of contributors.
  
  #include <sys/types.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include "db/db_impl.h"
  #include "db/column_db.h"
  #include "db/version_set.h"
  #include "leveldb/cache.h"
  #include "leveldb/db.h"
  #include "leveldb/env.h"
  #include "leveldb/write_batch.h"
  #include "port/port.h"
  #include "util/crc32c.h"
  #include "util/histogram.h"
  #include "util/mutexlock.h"
  #include "util/random.h"
  #include "util/testutil.h"
  
  // Comma-separated list of operations to run in the specified order
  //   Actual benchmarks:
  //      fillseq       -- write N values in sequential key order in async mode
  //      fillrandom    -- write N values in random key order in async mode
  //      overwrite     -- overwrite N values in random key order in async mode
  //      fillsync      -- write N/100 values in random key order in sync mode
  //      fill100K      -- write N/1000 100K values in random order in async mode
  //      deleteseq     -- delete N keys in sequential order
  //      deleterandom  -- delete N keys in random order
  //      readseq       -- read N times sequentially
  //      readreverse   -- read N times in reverse order
  //      readrandom    -- read N times in random order
  //      readmissing   -- read N missing keys in random order
  //      readhot       -- read N times in random order from 1% section of DB
  //      seekrandom    -- N random seeks
  //      crc32c        -- repeated crc32c of 4K of data
  //      acquireload   -- load N*1000 times
  //   Meta operations:
  //      compact     -- Compact the entire DB
  //      stats       -- Print DB stats
  //      sstables    -- Print sstable info
  //      heapprofile -- Dump a heap profile (if supported by this port)
  static const char* FLAGS_benchmarks =
      "fillseq,"
      "fillsync,"
      "fillrandom,"
      "overwrite,"
      "readrandom,"
      "readrandom,"  // Extra run to allow previous compactions to quiesce
      "readseq,"
      "readreverse,"
      "compact,"
      "readrandom,"
      "readseq,"
      "readreverse,"
      "fill100K,"
      "crc32c,"
      "snappycomp,"
      "snappyuncomp,"
      "acquireload,"
      ;
  
  // Number of key/values to place in database
  static int FLAGS_num = 1000000;
  
  static int FLAGS_dbtype = 1;
  
  // Number of read operations to do.  If negative, do FLAGS_num reads.
  static int FLAGS_reads = -1;
  
  // Number of concurrent threads to run.
  static int FLAGS_threads = 1;
  
  // Size of each value
  static int FLAGS_value_size = 100;
  
  // Arrange to generate values that shrink to this fraction of
  // their original size after compression
  static double FLAGS_compression_ratio = 0.5;
  
  // Print histogram of operation timings
  static bool FLAGS_histogram = false;
  
  // Number of bytes to buffer in memtable before compacting
  // (initialized to default value by "main")
  static int FLAGS_write_buffer_size = 0;
  
  // Number of bytes to use as a cache of uncompressed data.
  // Negative means use default settings.
  static int FLAGS_cache_size = -1;
  
  // Maximum number of files to keep open at the same time (use default if == 0)
  static int FLAGS_open_files = 0;
  
  // Bloom filter bits per key.
  // Negative means use default settings.
  static int FLAGS_bloom_bits = -1;
  
  // If true, do not destroy the existing database.  If you set this
  // flag and also specify a benchmark that wants a fresh database, that
  // benchmark will fail.
  static bool FLAGS_use_existing_db = false;
  
  // Use the db with the following name.
  static const char* FLAGS_db = "/tmp/dbbench";
  
  static const char* FLAGS_env_name = "";
  
  namespace leveldb {
  
  static Env* env_ = NULL;
  
  namespace {
  
  // Helper for quickly generating random data.
  class RandomGenerator {
   private:
    std::string data_;
    int pos_;
  
   public:
    RandomGenerator() {
      // We use a limited amount of data over and over again and ensure
      // that it is larger than the compression window (32KB), and also
      // large enough to serve all typical value sizes we want to write.
      Random rnd(301);
      std::string piece;
      while (data_.size() < 1048576) {
        // Add a short fragment that is as compressible as specified
        // by FLAGS_compression_ratio.
        test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
        data_.append(piece);
      }
      pos_ = 0;
    }
  
    Slice Generate(int len) {
      if (pos_ + len > data_.size()) {
        pos_ = 0;
        assert(len < data_.size());
      }
      pos_ += len;
      return Slice(data_.data() + pos_ - len, len);
    }
  };
  
  static Slice TrimSpace(Slice s) {
    int start = 0;
    while (start < s.size() && isspace(s[start])) {
      start++;
    }
    int limit = s.size();
    while (limit > start && isspace(s[limit-1])) {
      limit--;
    }
    return Slice(s.data() + start, limit - start);
  }
  
  static void AppendWithSpace(std::string* str, Slice msg) {
    if (msg.empty()) return;
    if (!str->empty()) {
      str->push_back(' ');
    }
    str->append(msg.data(), msg.size());
  }
  
  class Stats {
   private:
    double start_;
    double finish_;
    double seconds_;
    int done_;
    int next_report_;
    int64_t bytes_;
    double last_op_finish_;
    Histogram hist_;
    std::string message_;
  
   public:
    Stats() { Start(); }
  
    void Start() {
      next_report_ = 100;
      last_op_finish_ = start_;
      hist_.Clear();
      done_ = 0;
      bytes_ = 0;
      seconds_ = 0;
      start_ = env_->NowMicros();
      finish_ = start_;
      message_.clear();
    }
  
    void Merge(const Stats& other) {
      hist_.Merge(other.hist_);
      done_ += other.done_;
      bytes_ += other.bytes_;
      seconds_ += other.seconds_;
      if (other.start_ < start_) start_ = other.start_;
      if (other.finish_ > finish_) finish_ = other.finish_;
  
      // Just keep the messages from one thread
      if (message_.empty()) message_ = other.message_;
    }
  
    void Stop() {
      finish_ = env_->NowMicros();
      seconds_ = (finish_ - start_) * 1e-6;
    }
  
    void AddMessage(Slice msg) {
      AppendWithSpace(&message_, msg);
    }
  
    void FinishedSingleOp() {
      if (FLAGS_histogram) {
        double now = env_->NowMicros();
        double micros = now - last_op_finish_;
        hist_.Add(micros);
        if (micros > 20000) {
          fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
          fflush(stderr);
        }
        last_op_finish_ = now;
      }
  
      done_++;
      if (done_ >= next_report_) {
        if      (next_report_ < 1000)   next_report_ += 100;
        else if (next_report_ < 5000)   next_report_ += 500;
        else if (next_report_ < 10000)  next_report_ += 1000;
        else if (next_report_ < 50000)  next_report_ += 5000;
        else if (next_report_ < 100000) next_report_ += 10000;
        else if (next_report_ < 500000) next_report_ += 50000;
        else                            next_report_ += 100000;
        fprintf(stderr, "... finished %d ops%30s\r", done_, "");
        fflush(stderr);
      }
    }
  
    void AddBytes(int64_t n) {
      bytes_ += n;
    }
  
    void Report(const Slice& name) {
      // Pretend at least one op was done in case we are running a benchmark
      // that does not call FinishedSingleOp().
      if (done_ < 1) done_ = 1;
  
      std::string extra;
      if (bytes_ > 0) {
        // Rate is computed on actual elapsed time, not the sum of per-thread
        // elapsed times.
        double elapsed = (finish_ - start_) * 1e-6;
        char rate[100];
        snprintf(rate, sizeof(rate), "%6.1f MB/s",
                 (bytes_ / 1048576.0) / elapsed);
        extra = rate;
      }
      AppendWithSpace(&extra, message_);
  
      fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
              name.ToString().c_str(),
              seconds_ * 1e6 / done_,
              (extra.empty() ? "" : " "),
              extra.c_str());
      if (FLAGS_histogram) {
        fprintf(stdout, "Microseconds per op:\n%s\n", hist_.ToString().c_str());
      }
      fflush(stdout);
    }
  };
  
  // State shared by all concurrent executions of the same benchmark.
  struct SharedState {
    port::Mutex mu;
    port::CondVar cv;
    int total;
  
    // Each thread goes through the following states:
    //    (1) initializing
    //    (2) waiting for others to be initialized
    //    (3) running
    //    (4) done
  
    int num_initialized;
    int num_done;
    bool start;
  
    SharedState() : cv(&mu) { }
  };
  
  // Per-thread state for concurrent executions of the same benchmark.
  struct ThreadState {
    int tid;             // 0..n-1 when running in n threads
    Random rand;         // Has different seeds for different threads
    Stats stats;
    SharedState* shared;
  
    ThreadState(int index)
        : tid(index),
          rand(1000 + index) {
    }
  };
  
  }  // namespace
  
  class Benchmark {
   private:
    Cache* cache_;
    const FilterPolicy* filter_policy_;
    DB* db_;
    int num_;
    int value_size_;
    int entries_per_batch_;
    WriteOptions write_options_;
    int reads_;
    int heap_counter_;
  
    void PrintHeader() {
      const int kKeySize = 16;
      PrintEnvironment();
      if (FLAGS_dbtype == 1) {
        fprintf(stdout, "Database:   Normal LevelDB\n");
      } else {
        fprintf(stdout, "Database:   Column LevelDB\n");
      }
      fprintf(stdout, "Keys:       %d bytes each\n", kKeySize);
      fprintf(stdout, "Values:     %d bytes each (%d bytes after compression)\n",
              FLAGS_value_size,
              static_cast<int>(FLAGS_value_size * FLAGS_compression_ratio + 0.5));
      fprintf(stdout, "Entries:    %d\n", num_);
      fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
              ((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_)
               / 1048576.0));
      fprintf(stdout, "FileSize:   %.1f MB (estimated)\n",
              (((kKeySize + FLAGS_value_size * FLAGS_compression_ratio) * num_)
               / 1048576.0));
      PrintWarnings();
      fprintf(stdout, "------------------------------------------------\n");
    }
  
    void PrintWarnings() {
  #if defined(__GNUC__) && !defined(__OPTIMIZE__)
      fprintf(stdout,
              "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n"
              );
  #endif
  #ifndef NDEBUG
      fprintf(stdout,
              "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
  #endif
  
      // See if snappy is working by attempting to compress a compressible string
      const char text[] = "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy";
      std::string compressed;
      if (!port::Snappy_Compress(text, sizeof(text), &compressed)) {
        fprintf(stdout, "WARNING: Snappy compression is not enabled\n");
      } else if (compressed.size() >= sizeof(text)) {
        fprintf(stdout, "WARNING: Snappy compression is not effective\n");
      }
    }
  
    void PrintEnvironment() {
      fprintf(stderr, "LevelDB:    version %d.%d\n",
              kMajorVersion, kMinorVersion);
  
  #if defined(__linux)
      time_t now = time(NULL);
      fprintf(stderr, "Date:       %s", ctime(&now));  // ctime() adds newline
  
      FILE* cpuinfo = fopen("/proc/cpuinfo", "r");
      if (cpuinfo != NULL) {
        char line[1000];
        int num_cpus = 0;
        std::string cpu_type;
        std::string cache_size;
        while (fgets(line, sizeof(line), cpuinfo) != NULL) {
          const char* sep = strchr(line, ':');
          if (sep == NULL) {
            continue;
          }
          Slice key = TrimSpace(Slice(line, sep - 1 - line));
          Slice val = TrimSpace(Slice(sep + 1));
          if (key == "model name") {
            ++num_cpus;
            cpu_type = val.ToString();
          } else if (key == "cache size") {
            cache_size = val.ToString();
          }
        }
        fclose(cpuinfo);
        fprintf(stderr, "CPU:        %d * %s\n", num_cpus, cpu_type.c_str());
        fprintf(stderr, "CPUCache:   %s\n", cache_size.c_str());
      }
  #endif
    }
  
   public:
    Benchmark()
    : cache_(FLAGS_cache_size >= 0 ? NewLRUCache(FLAGS_cache_size) : NULL),
      filter_policy_(FLAGS_bloom_bits >= 0
                     ? NewZigzagFilterPolicy(FLAGS_bloom_bits)
                     : NULL),
      db_(NULL),
      num_(FLAGS_num),
      value_size_(FLAGS_value_size),
      entries_per_batch_(1),
      reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
      heap_counter_(0) {
      std::vector<std::string> files;
      env_->GetChildren(FLAGS_db, &files);
      for (int i = 0; i < files.size(); i++) {
        if (Slice(files[i]).starts_with("heap-")) {
          env_->DeleteFile(std::string(FLAGS_db) + "/" + files[i]);
        }
      }
      if (!FLAGS_use_existing_db) {
        DestroyDB(FLAGS_db, Options());
      }
    }
  
    ~Benchmark() {
      delete db_;
      delete cache_;
      delete filter_policy_;
    }
  
    void Run() {
      PrintHeader();
      Open();
  
      const char* benchmarks = FLAGS_benchmarks;
      while (benchmarks != NULL) {
        const char* sep = strchr(benchmarks, ',');
        Slice name;
        if (sep == NULL) {
          name = benchmarks;
          benchmarks = NULL;
        } else {
          name = Slice(benchmarks, sep - benchmarks);
          benchmarks = sep + 1;
        }
  
        // Reset parameters that may be overriddden bwlow
        num_ = FLAGS_num;
        reads_ = (FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads);
        value_size_ = FLAGS_value_size;
        entries_per_batch_ = 1;
        write_options_ = WriteOptions();
  
        void (Benchmark::*method)(ThreadState*) = NULL;
        bool fresh_db = false;
        int num_threads = FLAGS_threads;
  
        if (name == Slice("fillseq")) {
          fresh_db = true;
          method = &Benchmark::WriteSeq;
        } else if (name == Slice("fillbatch")) {
          fresh_db = true;
          entries_per_batch_ = 1000;
          method = &Benchmark::WriteSeq;
        } else if (name == Slice("fillrandom")) {
          fresh_db = true;
          method = &Benchmark::WriteRandom;
        } else if (name == Slice("overwrite")) {
          fresh_db = false;
          method = &Benchmark::WriteRandom;
        } else if (name == Slice("fillsync")) {
          fresh_db = true;
          num_ /= 1000;
          write_options_.sync = true;
          method = &Benchmark::WriteRandom;
        } else if (name == Slice("fill100K")) {
          fresh_db = true;
          num_ /= 1000;
          value_size_ = 100 * 1000;
          method = &Benchmark::WriteRandom;
        } else if (name == Slice("readseq")) {
          method = &Benchmark::ReadSequential;
        } else if (name == Slice("readreverse")) {
          method = &Benchmark::ReadReverse;
        } else if (name == Slice("readrandom")) {
          method = &Benchmark::ReadRandom;
        } else if (name == Slice("readmissing")) {
          method = &Benchmark::ReadMissing;
        } else if (name == Slice("seekrandom")) {
          method = &Benchmark::SeekRandom;
        } else if (name == Slice("readhot")) {
          method = &Benchmark::ReadHot;
        } else if (name == Slice("readrandomsmall")) {
          reads_ /= 1000;
          method = &Benchmark::ReadRandom;
        } else if (name == Slice("deleteseq")) {
          method = &Benchmark::DeleteSeq;
        } else if (name == Slice("deleterandom")) {
          method = &Benchmark::DeleteRandom;
        } else if (name == Slice("readwhilewriting")) {
          num_threads++;  // Add extra thread for writing
          method = &Benchmark::ReadWhileWriting;
        } else if (name == Slice("compact")) {
          method = &Benchmark::Compact;
        } else if (name == Slice("crc32c")) {
          method = &Benchmark::Crc32c;
        } else if (name == Slice("acquireload")) {
          method = &Benchmark::AcquireLoad;
        } else if (name == Slice("snappycomp")) {
          method = &Benchmark::SnappyCompress;
        } else if (name == Slice("snappyuncomp")) {
          method = &Benchmark::SnappyUncompress;
        } else if (name == Slice("heapprofile")) {
          HeapProfile();
        } else if (name == Slice("stats")) {
          PrintStats("leveldb.stats");
        } else if (name == Slice("sstables")) {
          PrintStats("leveldb.sstables");
        } else {
          if (name != Slice()) {  // No error message for empty name
            fprintf(stderr, "unknown benchmark '%s'\n", name.ToString().c_str());
          }
        }
  
        if (fresh_db) {
          if (FLAGS_use_existing_db) {
            fprintf(stdout, "%-12s : skipped (--use_existing_db is true)\n",
                    name.ToString().c_str());
            method = NULL;
          } else {
            delete db_;
            db_ = NULL;
            DestroyDB(FLAGS_db, Options());
            Open();
          }
        }
  
        if (method != NULL) {
          RunBenchmark(num_threads, name, method);
        }
      }
    }
  
   private:
    struct ThreadArg {
      Benchmark* bm;
      SharedState* shared;
      ThreadState* thread;
      void (Benchmark::*method)(ThreadState*);
    };
  
    static void ThreadBody(void* v) {
      ThreadArg* arg = reinterpret_cast<ThreadArg*>(v);
      SharedState* shared = arg->shared;
      ThreadState* thread = arg->thread;
      {
        MutexLock l(&shared->mu);
        shared->num_initialized++;
        if (shared->num_initialized >= shared->total) {
          shared->cv.SignalAll();
        }
        while (!shared->start) {
          shared->cv.Wait();
        }
      }
  
      thread->stats.Start();
      (arg->bm->*(arg->method))(thread);
      thread->stats.Stop();
  
      {
        MutexLock l(&shared->mu);
        shared->num_done++;
        if (shared->num_done >= shared->total) {
          shared->cv.SignalAll();
        }
      }
    }
  
    void RunBenchmark(int n, Slice name,
                      void (Benchmark::*method)(ThreadState*)) {
      SharedState shared;
      shared.total = n;
      shared.num_initialized = 0;
      shared.num_done = 0;
      shared.start = false;
  
      ThreadArg* arg = new ThreadArg[n];
      for (int i = 0; i < n; i++) {
        arg[i].bm = this;
        arg[i].method = method;
        arg[i].shared = &shared;
        arg[i].thread = new ThreadState(i);
        arg[i].thread->shared = &shared;
        env_->StartThread(ThreadBody, &arg[i]);
      }
  
      shared.mu.Lock();
      while (shared.num_initialized < n) {
        shared.cv.Wait();
      }
  
      shared.start = true;
      shared.cv.SignalAll();
      while (shared.num_done < n) {
        shared.cv.Wait();
      }
      shared.mu.Unlock();
  
      for (int i = 1; i < n; i++) {
        arg[0].thread->stats.Merge(arg[i].thread->stats);
      }
      arg[0].thread->stats.Report(name);
  
      for (int i = 0; i < n; i++) {
        delete arg[i].thread;
      }
      delete[] arg;
    }
  
    void Crc32c(ThreadState* thread) {
      // Checksum about 500MB of data total
      const int size = 4096;
      const char* label = "(4K per op)";
      std::string data(size, 'x');
      int64_t bytes = 0;
      uint32_t crc = 0;
      while (bytes < 500 * 1048576) {
        crc = crc32c::Value(data.data(), size);
        thread->stats.FinishedSingleOp();
        bytes += size;
      }
      // Print so result is not dead
      fprintf(stderr, "... crc=0x%x\r", static_cast<unsigned int>(crc));
  
      thread->stats.AddBytes(bytes);
      thread->stats.AddMessage(label);
    }
  
    void AcquireLoad(ThreadState* thread) {
      int dummy;
      port::AtomicPointer ap(&dummy);
      int count = 0;
      void *ptr = NULL;
      thread->stats.AddMessage("(each op is 1000 loads)");
      while (count < 100000) {
        for (int i = 0; i < 1000; i++) {
          ptr = ap.Acquire_Load();
        }
        count++;
        thread->stats.FinishedSingleOp();
      }
      if (ptr == NULL) exit(1); // Disable unused variable warning.
    }
  
    void SnappyCompress(ThreadState* thread) {
      RandomGenerator gen;
      Slice input = gen.Generate(Options().block_size);
      int64_t bytes = 0;
      int64_t produced = 0;
      bool ok = true;
      std::string compressed;
      while (ok && bytes < 1024 * 1048576) {  // Compress 1G
        ok = port::Snappy_Compress(input.data(), input.size(), &compressed);
        produced += compressed.size();
        bytes += input.size();
        thread->stats.FinishedSingleOp();
      }
  
      if (!ok) {
        thread->stats.AddMessage("(snappy failure)");
      } else {
        char buf[100];
        snprintf(buf, sizeof(buf), "(output: %.1f%%)",
                 (produced * 100.0) / bytes);
        thread->stats.AddMessage(buf);
        thread->stats.AddBytes(bytes);
      }
    }
  
    void SnappyUncompress(ThreadState* thread) {
      RandomGenerator gen;
      Slice input = gen.Generate(Options().block_size);
      std::string compressed;
      bool ok = port::Snappy_Compress(input.data(), input.size(), &compressed);
      int64_t bytes = 0;
      char* uncompressed = new char[input.size()];
      while (ok && bytes < 1024 * 1048576) {  // Compress 1G
        ok =  port::Snappy_Uncompress(compressed.data(), compressed.size(),
                                      uncompressed);
        bytes += input.size();
        thread->stats.FinishedSingleOp();
      }
      delete[] uncompressed;
  
      if (!ok) {
        thread->stats.AddMessage("(snappy failure)");
      } else {
        thread->stats.AddBytes(bytes);
      }
    }
  
    void Open() {
      assert(db_ == NULL);
      Options options;
      options.create_if_missing = !FLAGS_use_existing_db;
      options.block_cache = cache_;
      options.block_size = 32 * 1024;
      options.write_buffer_size = FLAGS_write_buffer_size;
      options.filter_policy = filter_policy_;
      options.disable_compaction = true;
      options.env = env_;
      Status s;
      if (FLAGS_dbtype == 1) {
        s = DB::Open(options, FLAGS_db, &db_);
      } else {
        db_ = new ColumnDB(options, FLAGS_db, s);
      }
      if (!s.ok()) {
        fprintf(stderr, "open error: %s\n", s.ToString().c_str());
        exit(1);
      }
    }
  
    void WriteSeq(ThreadState* thread) {
      DoWrite(thread, true);
    }
  
    void WriteRandom(ThreadState* thread) {
      DoWrite(thread, false);
    }
  
    void DoWrite(ThreadState* thread, bool seq) {
      if (num_ != FLAGS_num) {
        char msg[100];
        snprintf(msg, sizeof(msg), "(%d ops)", num_);
        thread->stats.AddMessage(msg);
      }
  
      RandomGenerator gen;
      WriteBatch batch;
      Status s;
      int64_t bytes = 0;
      for (int i = 0; i < num_; i += entries_per_batch_) {
        /*
        batch.Clear();
        for (int j = 0; j < entries_per_batch_; j++) {
          const int k = seq ? i+j : (thread->rand.Next() % FLAGS_num);
          char key[100];
          snprintf(key, sizeof(key), "%016d", k);
          batch.Put(key, gen.Generate(value_size_));
          bytes += value_size_ + strlen(key);
          thread->stats.FinishedSingleOp();
        }
        s = db_->Write(write_options_, &batch);
        */
        const int k = seq ? i : (thread->rand.Next() % FLAGS_num);
        char key[100];
        snprintf(key, sizeof(key), "%016d", k);
        db_->Put(write_options_, key, gen.Generate(value_size_));
        bytes += value_size_ + strlen(key);
        thread->stats.FinishedSingleOp();
  
        if (!s.ok()) {
          fprintf(stderr, "put error: %s\n", s.ToString().c_str());
          exit(1);
        }
      }
      thread->stats.AddBytes(bytes);
    }
  
    void ReadSequential(ThreadState* thread) {
      Iterator* iter = db_->NewIterator(ReadOptions());
      int i = 0;
      int64_t bytes = 0;
      for (iter->SeekToFirst(); i < reads_ && iter->Valid(); iter->Next()) {
        bytes += iter->key().size() + iter->value().size();
        thread->stats.FinishedSingleOp();
        ++i;
      }
      delete iter;
      thread->stats.AddBytes(bytes);
    }
  
    void ReadReverse(ThreadState* thread) {
      Iterator* iter = db_->NewIterator(ReadOptions());
      int i = 0;
      int64_t bytes = 0;
      for (iter->SeekToLast(); i < reads_ && iter->Valid(); iter->Prev()) {
        bytes += iter->key().size() + iter->value().size();
        thread->stats.FinishedSingleOp();
        ++i;
      }
      delete iter;
      thread->stats.AddBytes(bytes);
    }
  
    void ReadRandom(ThreadState* thread) {
      ReadOptions options;
      std::string value;
      int found = 0;
      for (int i = 0; i < reads_; i++) {
        char key[100];
        const int k = thread->rand.Next() % FLAGS_num;
        snprintf(key, sizeof(key), "%016d", k);
        if (db_->Get(options, key, &value).ok()) {
          found++;
        }
        thread->stats.FinishedSingleOp();
      }
      char msg[100];
      snprintf(msg, sizeof(msg), "(%d of %d found)", found, num_);
      thread->stats.AddMessage(msg);
    }
  
    void ReadMissing(ThreadState* thread) {
      ReadOptions options;
      std::string value;
      for (int i = 0; i < reads_; i++) {
        char key[100];
        const int k = thread->rand.Next() % FLAGS_num;
        snprintf(key, sizeof(key), "%016d.", k);
        db_->Get(options, key, &value);
        thread->stats.FinishedSingleOp();
      }
    }
  
    void ReadHot(ThreadState* thread) {
      ReadOptions options;
      std::string value;
      const int range = (FLAGS_num + 99) / 100;
      for (int i = 0; i < reads_; i++) {
        char key[100];
        const int k = thread->rand.Next() % range;
        snprintf(key, sizeof(key), "%016d", k);
        db_->Get(options, key, &value);
        thread->stats.FinishedSingleOp();
      }
    }
  
    void SeekRandom(ThreadState* thread) {
      ReadOptions options;
      std::string value;
      int found = 0;
      for (int i = 0; i < reads_; i++) {
        Iterator* iter = db_->NewIterator(options);
        char key[100];
        const int k = thread->rand.Next() % FLAGS_num;
        snprintf(key, sizeof(key), "%016d", k);
        iter->Seek(key);
        if (iter->Valid() && iter->key() == key) found++;
        delete iter;
        thread->stats.FinishedSingleOp();
      }
      char msg[100];
      snprintf(msg, sizeof(msg), "(%d of %d found)", found, num_);
      thread->stats.AddMessage(msg);
    }
  
    void DoDelete(ThreadState* thread, bool seq) {
      RandomGenerator gen;
      WriteBatch batch;
      Status s;
      for (int i = 0; i < num_; i += entries_per_batch_) {
        batch.Clear();
        for (int j = 0; j < entries_per_batch_; j++) {
          const int k = seq ? i+j : (thread->rand.Next() % FLAGS_num);
          char key[100];
          snprintf(key, sizeof(key), "%016d", k);
          batch.Delete(key);
          thread->stats.FinishedSingleOp();
        }
        s = db_->Write(write_options_, &batch);
        if (!s.ok()) {
          fprintf(stderr, "del error: %s\n", s.ToString().c_str());
          exit(1);
        }
      }
    }
  
    void DeleteSeq(ThreadState* thread) {
      DoDelete(thread, true);
    }
  
    void DeleteRandom(ThreadState* thread) {
      DoDelete(thread, false);
    }
  
    void ReadWhileWriting(ThreadState* thread) {
      if (thread->tid > 0) {
        ReadRandom(thread);
      } else {
        // Special thread that keeps writing until other threads are done.
        RandomGenerator gen;
        while (true) {
          {
            MutexLock l(&thread->shared->mu);
            if (thread->shared->num_done + 1 >= thread->shared->num_initialized) {
              // Other threads have finished
              break;
            }
          }
  
          const int k = thread->rand.Next() % FLAGS_num;
          char key[100];
          snprintf(key, sizeof(key), "%016d", k);
          Status s = db_->Put(write_options_, key, gen.Generate(value_size_));
          if (!s.ok()) {
            fprintf(stderr, "put error: %s\n", s.ToString().c_str());
            exit(1);
          }
        }
  
        // Do not count any of the preceding work/delay in stats.
        thread->stats.Start();
      }
    }
  
    void Compact(ThreadState* thread) {
      db_->CompactRange(NULL, NULL);
    }
  
    void PrintStats(const char* key) {
      std::string stats;
      if (!db_->GetProperty(key, &stats)) {
        stats = "(failed)";
      }
      fprintf(stdout, "\n%s\n", stats.c_str());
    }
  
    static void WriteToFile(void* arg, const char* buf, int n) {
      reinterpret_cast<WritableFile*>(arg)->Append(Slice(buf, n));
    }
  
    void HeapProfile() {
      char fname[100];
      snprintf(fname, sizeof(fname), "%s/heap-%04d", FLAGS_db, ++heap_counter_);
      WritableFile* file;
      Status s = env_->NewWritableFile(fname, &file);
      if (!s.ok()) {
        fprintf(stderr, "%s\n", s.ToString().c_str());
        return;
      }
      bool ok = port::GetHeapProfile(WriteToFile, file);
      delete file;
      if (!ok) {
        fprintf(stderr, "heap profiling not supported\n");
        env_->DeleteFile(fname);
      }
    }
  };
  
  }  // namespace leveldb
  
  int main(int argc, char** argv) {
    FLAGS_write_buffer_size = leveldb::Options().write_buffer_size;
    FLAGS_open_files = leveldb::Options().max_open_files;
  
    for (int i = 1; i < argc; i++) {
      double d;
      int n;
      char junk;
      if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
        FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
      } else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
        FLAGS_compression_ratio = d;
      } else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
                 (n == 0 || n == 1)) {
        FLAGS_histogram = n;
      } else if (sscanf(argv[i], "--use_existing_db=%d%c", &n, &junk) == 1 &&
                 (n == 0 || n == 1)) {
        FLAGS_use_existing_db = n;
      } else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
        FLAGS_num = n;
      } else if (sscanf(argv[i], "--dbtype=%d%c", &n, &junk) == 1) {
        FLAGS_dbtype = n;
      } else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
        FLAGS_reads = n;
      } else if (sscanf(argv[i], "--threads=%d%c", &n, &junk) == 1) {
        FLAGS_threads = n;
      } else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
        FLAGS_value_size = n;
      } else if (sscanf(argv[i], "--write_buffer_size=%d%c", &n, &junk) == 1) {
        FLAGS_write_buffer_size = n;
      } else if (sscanf(argv[i], "--cache_size=%d%c", &n, &junk) == 1) {
        FLAGS_cache_size = n;
      } else if (sscanf(argv[i], "--bloom_bits=%d%c", &n, &junk) == 1) {
        FLAGS_bloom_bits = n;
      } else if (sscanf(argv[i], "--open_files=%d%c", &n, &junk) == 1) {
        FLAGS_open_files = n;
      } else if (strncmp(argv[i], "--db=", 5) == 0) {
        FLAGS_db = argv[i] + 5;
      } else if (strncmp(argv[i], "--env=", 6) == 0) {
        FLAGS_env_name = argv[i] + 6;
      } else {
        fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
        exit(1);
      }
    }
  
    if (strncmp(FLAGS_env_name, "hdfs", 4) == 0) {
      leveldb::env_ = leveldb::Env::HDFSEnv(NULL, 8020);
    } else
    if (strncmp(FLAGS_env_name, "pvfs", 4) == 0) {
      leveldb::env_ = leveldb::Env::PVFSEnv();
    } else {
      leveldb::env_ = leveldb::Env::Default();
    }
    leveldb::Benchmark benchmark;
    benchmark.Run();
    return 0;
  }
  