common/perf_counter.h

/*
Copyright 2022 The Photon Authors

Licensed 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,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#pragma once
#include <cstdint>
#include <cinttypes>
#include <atomic>

struct __perf_counter;

extern "C"
{
    void init_perf_counter(__perf_counter* pc);
}

enum PerfType
{
    TOTAL = 0,
    ACCUMULATE,
    AVERAGE,
};

#define DEFAULT_INTERVAL 5

struct __perf_counter
{
    const char* _name;
    std::atomic<uint64_t> _value;
    const PerfType _type;
    const int _name_length;
    const int _interval;
    __perf_counter* _next;
    uint64_t _last;

    template<int N>
    constexpr __perf_counter(const char (&name)[N], PerfType type,
        int interval = DEFAULT_INTERVAL) : _name(name), _value(0),
            _type(type), _name_length(N - 1), _interval(interval), _last(0)
    {
        static_assert(sizeof(_type) == 4, "...");
    }

    void add(uint64_t dx)
    {
#ifdef PERF
        if (_type == AVERAGE)
            dx = (dx << 24) + 1;
        _value.fetch_add(dx, std::memory_order_relaxed);
#endif
    }
};

struct __PCR
{
    __PCR(__perf_counter* pc)
    {
#ifdef PERF
        init_perf_counter(pc);
#endif
    }
};

#define REGISTER_PERF(NAME, ...) \
    static __perf_counter __g_PC_##NAME(#NAME, __VA_ARGS__); \
    static __PCR __pcr##NAME( &__g_PC_##NAME );

#define REPORT_PERF(NAME, VALUE) __g_PC_##NAME.add(VALUE);