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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2011 New Dream Network
+ * Copyright (C) 2017 OVH
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software 
+ * Foundation.  See file COPYING.
+ * 
+ */
+
+
+#ifndef CEPH_COMMON_PERF_COUNTERS_H
+#define CEPH_COMMON_PERF_COUNTERS_H
+
+#include <string>
+#include <vector>
+#include <memory>
+#include <atomic>
+#include <cstdint>
+
+#include "common/perf_histogram.h"
+#include "include/utime.h"
+#include "include/common_fwd.h"
+#include "common/ceph_mutex.h"
+#include "common/ceph_time.h"
+
+namespace TOPNSPC::common {
+  class CephContext;
+  class PerfCountersBuilder;
+  class PerfCounters;
+}
+
+enum perfcounter_type_d : uint8_t
+{
+  PERFCOUNTER_NONE = 0,
+  PERFCOUNTER_TIME = 0x1,       // float (measuring seconds)
+  PERFCOUNTER_U64 = 0x2,        // integer (note: either TIME or U64 *must* be set)
+  PERFCOUNTER_LONGRUNAVG = 0x4, // paired counter + sum (time)
+  PERFCOUNTER_COUNTER = 0x8,    // counter (vs gauge)
+  PERFCOUNTER_HISTOGRAM = 0x10, // histogram (vector) of values
+};
+
+enum unit_t : uint8_t
+{
+  UNIT_BYTES,
+  UNIT_NONE
+};
+
+/* Class for constructing a PerfCounters object.
+ *
+ * This class performs some validation that the parameters we have supplied are
+ * correct in create_perf_counters().
+ *
+ * In the future, we will probably get rid of the first/last arguments, since
+ * PerfCountersBuilder can deduce them itself.
+ */
+namespace TOPNSPC::common {
+class PerfCountersBuilder
+{
+public:
+  PerfCountersBuilder(CephContext *cct, const std::string &name,
+		    int first, int last);
+  ~PerfCountersBuilder();
+
+  // prio values: higher is better, and higher values get included in
+  // 'ceph daemonperf' (and similar) results.
+  // Use of priorities enables us to add large numbers of counters
+  // internally without necessarily overwhelming consumers.
+  enum {
+    PRIO_CRITICAL = 10,
+    // 'interesting' is the default threshold for `daemonperf` output
+    PRIO_INTERESTING = 8,
+    // `useful` is the default threshold for transmission to ceph-mgr
+    // and inclusion in prometheus/influxdb plugin output
+    PRIO_USEFUL = 5,
+    PRIO_UNINTERESTING = 2,
+    PRIO_DEBUGONLY = 0,
+  };
+  void add_u64(int key, const char *name,
+	       const char *description=NULL, const char *nick = NULL,
+	       int prio=0, int unit=UNIT_NONE);
+  void add_u64_counter(int key, const char *name,
+		       const char *description=NULL,
+		       const char *nick = NULL,
+		       int prio=0, int unit=UNIT_NONE);
+  void add_u64_avg(int key, const char *name,
+		   const char *description=NULL,
+		   const char *nick = NULL,
+		   int prio=0, int unit=UNIT_NONE);
+  void add_time(int key, const char *name,
+		const char *description=NULL,
+		const char *nick = NULL,
+		int prio=0);
+  void add_time_avg(int key, const char *name,
+		    const char *description=NULL,
+		    const char *nick = NULL,
+		    int prio=0);
+  void add_u64_counter_histogram(
+    int key, const char* name,
+    PerfHistogramCommon::axis_config_d x_axis_config,
+    PerfHistogramCommon::axis_config_d y_axis_config,
+    const char *description=NULL,
+    const char* nick = NULL,
+    int prio=0, int unit=UNIT_NONE);
+
+  void set_prio_default(int prio_)
+  {
+    prio_default = prio_;
+  }
+
+  PerfCounters* create_perf_counters();
+private:
+  PerfCountersBuilder(const PerfCountersBuilder &rhs);
+  PerfCountersBuilder& operator=(const PerfCountersBuilder &rhs);
+  void add_impl(int idx, const char *name,
+                const char *description, const char *nick, int prio, int ty, int unit=UNIT_NONE,
+                std::unique_ptr<PerfHistogram<>> histogram = nullptr);
+
+  PerfCounters *m_perf_counters;
+
+  int prio_default = 0;
+};
+
+/*
+ * A PerfCounters object is usually associated with a single subsystem.
+ * It contains counters which we modify to track performance and throughput
+ * over time. 
+ *
+ * PerfCounters can track several different types of values:
+ * 1) integer values & counters
+ * 2) floating-point values & counters
+ * 3) floating-point averages
+ * 4) 2D histograms of quantized value pairs
+ *
+ * The difference between values, counters and histograms is in how they are initialized
+ * and accessed. For a counter, use the inc(counter, amount) function (note
+ * that amount defaults to 1 if you don't set it). For a value, use the
+ * set(index, value) function. For histogram use the hinc(value1, value2) function.
+ * (For time, use the tinc and tset variants.)
+ *
+ * If for some reason you would like to reset your counters, you can do so using
+ * the set functions even if they are counters, and you can also
+ * increment your values if for some reason you wish to.
+ *
+ * For the time average, it returns the current value and
+ * the "avgcount" member when read off. avgcount is incremented when you call
+ * tinc. Calling tset on an average is an error and will assert out.
+ */
+class PerfCounters
+{
+public:
+  /** Represents a PerfCounters data element. */
+  struct perf_counter_data_any_d {
+    perf_counter_data_any_d()
+      : name(NULL),
+        description(NULL),
+        nick(NULL),
+	 type(PERFCOUNTER_NONE),
+	 unit(UNIT_NONE)
+    {}
+    perf_counter_data_any_d(const perf_counter_data_any_d& other)
+      : name(other.name),
+        description(other.description),
+        nick(other.nick),
+	 type(other.type),
+	 unit(other.unit),
+	 u64(other.u64.load()) {
+      auto a = other.read_avg();
+      u64 = a.first;
+      avgcount = a.second;
+      avgcount2 = a.second;
+      if (other.histogram) {
+        histogram.reset(new PerfHistogram<>(*other.histogram));
+      }
+    }
+
+    const char *name;
+    const char *description;
+    const char *nick;
+    uint8_t prio = 0;
+    enum perfcounter_type_d type;
+    enum unit_t unit;
+    std::atomic<uint64_t> u64 = { 0 };
+    std::atomic<uint64_t> avgcount = { 0 };
+    std::atomic<uint64_t> avgcount2 = { 0 };
+    std::unique_ptr<PerfHistogram<>> histogram;
+
+    void reset()
+    {
+      if (type != PERFCOUNTER_U64) {
+	    u64 = 0;
+	    avgcount = 0;
+	    avgcount2 = 0;
+      }
+      if (histogram) {
+        histogram->reset();
+      }
+    }
+
+    // read <sum, count> safely by making sure the post- and pre-count
+    // are identical; in other words the whole loop needs to be run
+    // without any intervening calls to inc, set, or tinc.
+    std::pair<uint64_t,uint64_t> read_avg() const {
+      uint64_t sum, count;
+      do {
+	count = avgcount2;
+	sum = u64;
+      } while (avgcount != count);
+      return { sum, count };
+    }
+  };
+
+  template <typename T>
+  struct avg_tracker {
+    std::pair<uint64_t, T> last;
+    std::pair<uint64_t, T> cur;
+    avg_tracker() : last(0, 0), cur(0, 0) {}
+    T current_avg() const {
+      if (cur.first == last.first)
+        return 0;
+      return (cur.second - last.second) / (cur.first - last.first);
+    }
+    void consume_next(const std::pair<uint64_t, T> &next) {
+      last = cur;
+      cur = next;
+    }
+  };
+
+  ~PerfCounters();
+
+  void inc(int idx, uint64_t v = 1);
+  void dec(int idx, uint64_t v = 1);
+  void set(int idx, uint64_t v);
+  uint64_t get(int idx) const;
+
+  void tset(int idx, utime_t v);
+  void tinc(int idx, utime_t v);
+  void tinc(int idx, ceph::timespan v);
+  utime_t tget(int idx) const;
+
+  void hinc(int idx, int64_t x, int64_t y);
+
+  void reset();
+  void dump_formatted(ceph::Formatter *f, bool schema,
+                      const std::string &counter = "") const {
+    dump_formatted_generic(f, schema, false, counter);
+  }
+  void dump_formatted_histograms(ceph::Formatter *f, bool schema,
+                                 const std::string &counter = "") const {
+    dump_formatted_generic(f, schema, true, counter);
+  }
+  std::pair<uint64_t, uint64_t> get_tavg_ns(int idx) const;
+
+  const std::string& get_name() const;
+  void set_name(std::string s) {
+    m_name = s;
+  }
+
+  /// adjust priority values by some value
+  void set_prio_adjust(int p) {
+    prio_adjust = p;
+  }
+
+  int get_adjusted_priority(int p) const {
+    return std::max(std::min(p + prio_adjust,
+                             (int)PerfCountersBuilder::PRIO_CRITICAL),
+                    0);
+  }
+
+private:
+  PerfCounters(CephContext *cct, const std::string &name,
+	     int lower_bound, int upper_bound);
+  PerfCounters(const PerfCounters &rhs);
+  PerfCounters& operator=(const PerfCounters &rhs);
+  void dump_formatted_generic(ceph::Formatter *f, bool schema, bool histograms,
+                              const std::string &counter = "") const;
+
+  typedef std::vector<perf_counter_data_any_d> perf_counter_data_vec_t;
+
+  CephContext *m_cct;
+  int m_lower_bound;
+  int m_upper_bound;
+  std::string m_name;
+
+  int prio_adjust = 0;
+
+#if !defined(WITH_SEASTAR) || defined(WITH_ALIEN)
+  const std::string m_lock_name;
+  /** Protects m_data */
+  ceph::mutex m_lock;
+#endif
+
+  perf_counter_data_vec_t m_data;
+
+  friend class PerfCountersBuilder;
+  friend class PerfCountersCollectionImpl;
+};
+
+class SortPerfCountersByName {
+public:
+  bool operator()(const PerfCounters* lhs, const PerfCounters* rhs) const {
+    return (lhs->get_name() < rhs->get_name());
+  }
+};
+
+typedef std::set <PerfCounters*, SortPerfCountersByName> perf_counters_set_t;
+
+/*
+ * PerfCountersCollectionImp manages PerfCounters objects for a Ceph process.
+ */
+class PerfCountersCollectionImpl
+{
+public:
+  PerfCountersCollectionImpl();
+  ~PerfCountersCollectionImpl();
+  void add(PerfCounters *l);
+  void remove(PerfCounters *l);
+  void clear();
+  bool reset(const std::string &name);
+
+  void dump_formatted(ceph::Formatter *f, bool schema,
+                      const std::string &logger = "",
+                      const std::string &counter = "") const {
+    dump_formatted_generic(f, schema, false, logger, counter);
+  }
+
+  void dump_formatted_histograms(ceph::Formatter *f, bool schema,
+                                 const std::string &logger = "",
+                                 const std::string &counter = "") const {
+    dump_formatted_generic(f, schema, true, logger, counter);
+  }
+
+  // A reference to a perf_counter_data_any_d, with an accompanying
+  // pointer to the enclosing PerfCounters, in order that the consumer
+  // can see the prio_adjust
+  class PerfCounterRef
+  {
+    public:
+    PerfCounters::perf_counter_data_any_d *data;
+    PerfCounters *perf_counters;
+  };
+  typedef std::map<std::string,
+          PerfCounterRef> CounterMap;
+
+  void with_counters(std::function<void(const CounterMap &)>) const;
+
+private:
+  void dump_formatted_generic(ceph::Formatter *f, bool schema, bool histograms,
+                              const std::string &logger = "",
+                              const std::string &counter = "") const;
+
+  perf_counters_set_t m_loggers;
+
+  CounterMap by_path; 
+};
+
+
+class PerfGuard {
+  const ceph::real_clock::time_point start;
+  PerfCounters* const counters;
+  const int event;
+
+public:
+  PerfGuard(PerfCounters* const counters,
+            const int event)
+  : start(ceph::real_clock::now()),
+    counters(counters),
+    event(event) {
+  }
+
+  ~PerfGuard() {
+    counters->tinc(event, ceph::real_clock::now() - start);
+  }
+};
+
+}
+#endif