rocksdb/util/histogram.h
gabor@google.com e3584f9c28 Bugfix for issue 33; reduce lock contention in Get(), parallel benchmarks.
- Fix for issue 33 (non-null-terminated result from
  leveldb_property_value())

- Support for running multiple instances of a benchmark in parallel.

- Reduce lock contention on Get():
  (1) Do not hold the lock while searching memtables.
  (2) Shard block and table caches 16-ways.

  Benchmark for evaluating this change:
  $ db_bench --benchmarks=fillseq1,readrandom --threads=$n
  (fillseq1 is a small hack to make sure fillseq runs once regardless
  of number of threads specified on the command line).



git-svn-id: https://leveldb.googlecode.com/svn/trunk@49 62dab493-f737-651d-591e-8d6aee1b9529
2011-08-22 21:08:51 +00:00

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// 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.
#ifndef STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
#define STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
#include <string>
namespace leveldb {
class Histogram {
public:
Histogram() { }
~Histogram() { }
void Clear();
void Add(double value);
void Merge(const Histogram& other);
std::string ToString() const;
private:
double min_;
double max_;
double num_;
double sum_;
double sum_squares_;
enum { kNumBuckets = 154 };
static const double kBucketLimit[kNumBuckets];
double buckets_[kNumBuckets];
double Median() const;
double Percentile(double p) const;
double Average() const;
double StandardDeviation() const;
};
}
#endif // STORAGE_LEVELDB_UTIL_HISTOGRAM_H_