test pthread_create

test-threads-v2.cpp

#include <cstdint>
#include <ctime>
#include <iostream>
#include <sys/types.h>
#include <thread>
#include <list>

uint64_t now_ns()
{
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
    return ts.tv_sec * (uint64_t)1e9 + ts.tv_nsec;
}

template <class F>
uint64_t elapsed(const F & f)
{
    uint64_t start = now_ns();
    f();
    uint64_t end = now_ns();
    return end - start;
}

int main()
{
    std::list<std::thread> threads;

    {
        uint64_t create_took = elapsed([&]() {
            for (int i = 0; i < 30e3; ++i)
            {
                try
                {
                    threads.emplace_back([]() {});
                }
                catch (...)
                {
                    std::cerr << "Cannot create thread " << i << ". Breaking\n";
                    break;
                }
            }
        });
        std::cerr << "join: took " << create_took/1e6 << "ms, rate: " << threads.size()/((double)create_took/1e9) << " TPS\n";
    }

    {
        uint64_t join_took = elapsed([&]() {
            for (auto & thread : threads)
                thread.join();
        });
        std::cerr << "join: took " << join_took/1e6 << "ms, rate: " << threads.size()/((double)join_took/1e9) << " TPS\n";
    }
}

test-threads-v2.log

$ clang++ /tmp/test-threads.cpp -o /tmp/test-threads -O3 && time /tmp/test-threads
join: took 592.951ms, rate: 50594.4 TPS
join: took 136.108ms, rate: 220414 TPS

real    0m0.734s
user    0m0.054s
sys     0m0.678s

$ clang++ /tmp/test-threads.cpp -o /tmp/test-threads -O3 && time /tmp/test-threads
join: took 582.641ms, rate: 51489.7 TPS
detach: took 135.038ms, rate: 222160 TPS

real    0m0.722s
user    0m0.068s
sys     0m0.654s

test-threads.cpp

#include <thread>

int main()
{
    for (int i = 0; i < 50e3; ++i) {
        std::thread t([]() {});
        t.join();
    }
}

test-threads.log

$ clang++ /tmp/test-threads.cpp -o /tmp/test-threads -O3 && time /tmp/test-threads

real    0m1.201s
user    0m0.079s
sys     0m0.723s