source: benchmark/readyQ/yield.cpp@ a1b9bc3

#include <cassert>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <climits>

extern "C" {
        #include <locale.h>
        #include <getopt.h>
}

#include <unistd.h>

#include <chrono>

using Clock = std::chrono::high_resolution_clock;
using duration_t = std::chrono::duration<double>;
using std::chrono::nanoseconds;


template<typename Ratio, typename T>
T duration_cast(T seconds) {
        return std::chrono::duration_cast<std::chrono::duration<T, Ratio>>(std::chrono::duration<T>(seconds)).count();
}

volatile bool run = false;
volatile unsigned long long global_counter;

#include "libfibre/fibre.h"

FibreBarrier * barrier;
struct __attribute__((aligned(128))) counter_t {
        int value = 0;
};

void fibre_main( counter_t * counter ) {
        barrier->wait();
        // /* paranoid */ assert( true == __atomic_load_n(&run, __ATOMIC_RELAXED) );

        while(__atomic_load_n(&run, __ATOMIC_RELAXED)) {
                Fibre::forceYield();
                // fibre_yield();
                counter->value++;
        }
        __atomic_fetch_add(&global_counter, counter->value, __ATOMIC_SEQ_CST);
}

int main(int argc, char * argv[]) {
        double duration = 5;
        int nprocs = 1;
        int nthreads = 1;

        std::cout.imbue(std::locale(""));
        setlocale(LC_ALL, "");

        for(;;) {
                static struct option options[] = {
                        {"duration",  required_argument, 0, 'd'},
                        {"nprocs",    required_argument, 0, 'p'},
                        {"nthreads",  required_argument, 0, 't'},
                        {0, 0, 0, 0}
                };

                int idx = 0;
                int opt = getopt_long(argc, argv, "d:p:t:", options, &idx);

                const char * arg = optarg ? optarg : "";
                size_t len = 0;
                char * end;
                switch(opt) {
                        case -1:
                                goto run;
                        // Numeric Arguments
                        case 'd':
                                duration = strtod(arg, &end);
                                if(*end != '\0') {
                                        fprintf(stderr, "Duration must be a valid double, was %s\n", arg);
                                        goto usage;
                                }
                                break;
                        case 't':
                                nthreads = strtoul(arg, &end, 10);
                                if(*end != '\0' || nthreads < 1) {
                                        fprintf(stderr, "Number of threads must be a positive integer, was %s\n", arg);
                                        goto usage;
                                }
                                break;
                        case 'p':
                                nprocs = strtoul(arg, &end, 10);
                                if(*end != '\0' || nprocs < 1) {
                                        fprintf(stderr, "Number of processors must be a positive integer, was %s\n", arg);
                                        goto usage;
                                }
                                break;
                        // Other cases
                        default: /* ? */
                                fprintf( stderr, "Unkown option '%c'\n", opt);
                        usage:
                                fprintf( stderr, "Usage: %s [options]\n", argv[0]);
                                fprintf( stderr, "\n" );
                                fprintf( stderr, "  -d, --duration=DURATION  Duration of the experiment, in seconds\n" );
                                fprintf( stderr, "  -t, --nthreads=NTHREADS  Number of kernel threads\n" );
                                fprintf( stderr, "  -q, --nqueues=NQUEUES    Number of queues per threads\n" );
                                exit(1);
                }
        }
        run:

        {
                printf("Running %d threads on %d processors for %lf seconds\n", nthreads, nprocs, duration);

                FibreInit();
                barrier = new FibreBarrier(nthreads + 1);
                {
                        Context::CurrCluster().addWorkers(nprocs);
                        {
                                counter_t counters[nthreads];
                                Fibre threads[nthreads];
                                for(int i = 0; i < nthreads; i++) {
                                        threads[i].run(fibre_main, &counters[i]);
                                }
                                printf("Starting\n");
                                bool is_tty = isatty(STDOUT_FILENO);
                                auto before = Clock::now();
                                run = true;

                                barrier->wait();
                                for(;;) {
                                        usleep(500'000);
                                        auto now = Clock::now();
                                        duration_t durr = now - before;
                                        if( durr.count() > duration ) {
                                                break;
                                        }
                                        if(is_tty) {
                                                std::cout << "\r" << std::setprecision(4) << durr.count();
                                                std::cout.flush();
                                        }
                                }

                                auto after = Clock::now();
                                duration_t durr = after - before;
                                duration = durr.count();
                                run = false;
                                printf("\nDone\n");
                                for(auto & thread : threads) {
                                        thread.join();
                                }

                                // for(const auto & counter : counters) {
                                //      std::cout << counter.value << std::endl;
                                // }
                        }
                }

                auto dur_nano = duration_cast<std::nano>(duration);

                std::cout << "Took " << duration << " s\n";
                printf("Total yields        : %'15llu\n", global_counter );
                printf("Yields per procs    : %'15llu\n", global_counter / nprocs );
                printf("Yields per second   : %'18.2lf\n", ((double)global_counter) / duration );
                printf("Yields/sec/procs    : %'18.2lf\n", (((double)global_counter) / nprocs) / duration );
                printf("ns per yields       : %'18.2lf\n", dur_nano / global_counter );
                printf("ns per yields/procs : %'18.2lf\n", dur_nano / (global_counter / nprocs) );

        }
}