condition-perf.cpp

#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <chrono>
#include <boost/thread/barrier.hpp>

using namespace std;
using clock_type = chrono::system_clock;

mutex              mtx;
condition_variable cond;
boost::barrier     bar{2};

clock_type::time_point before_notify;
clock_type::time_point after_wait;

void thrproc()
{
    unique_lock<mutex> lock{mtx};
    bar.count_down_and_wait();
    cond.wait(lock);
    after_wait = clock_type::now();
}

int main()
{
    auto thr = thread{thrproc};
    bar.count_down_and_wait();

    {
        lock_guard<mutex> lock{mtx};
        before_notify = clock_type::now();
        cond.notify_all();
    }

    thr.join();

    cout << chrono::duration_cast<chrono::microseconds>(after_wait - before_notify).count() << endl;
}

/*
% g++ --version                                                         
g++ (GCC) 5.3.1 20160406 (Red Hat 5.3.1-6)

% g++ -std=c++14 -O3 condition-perf.cpp -pthread -lboost_system -lboost_thread

CPU: Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz
Run iterations: 10000

sum:142385
avg:14.2385
std:10.4202791589285
med:14
max:76
min:2
*/