pipes_bench.cpp

#include <sched.h>
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <errno.h>
#include <thread>
#include <unistd.h>
#include "timers.h"

constexpr int iterations = 100000;
constexpr int items = 1000;

struct fd_pair {
  /*
     - pipefd[0] refers to the read end of the pipe.  
     - pipefd[1] refers to the write end of the pipe.
     */
  int fd[2];
};

struct fd_pair pipes_1;

int main(int args, char* argv[]) {
  if (pipe(pipes_1.fd) == -1) {
    fmt::print("{} pipe() error\n", __func__);
    exit(-1);
  }


  struct sched_param param;
  param.sched_priority = 1;
  if (sched_setscheduler(getpid(), SCHED_FIFO, &param))
    fprintf(stderr, "sched_setscheduler(): %s\n", strerror(errno));

  struct timespec ts;

  auto start_ns = time_ns(&ts);
  auto start = rdtsc();

  int buf = 0;
  for (int i = 0; i < iterations; i++) {
    [[maybe_unused]] auto ret  = write(pipes_1.fd[1], &buf, 1);
    while (read(pipes_1.fd[0], &buf, 1) < 0) {};

  }

  auto delta_cycles = rdtsc() - start;
  auto delta = time_ns(&ts) - start_ns;

  constexpr int nswitches = iterations << 2;
  fmt::print("{}\tctx_switches={}\ttime={}ns\t{}ns/ctxsw\tcycles={}\t\n", __func__,
      nswitches, delta, (delta / (float) nswitches), delta_cycles);

  close(pipes_1.fd[0]);
  close(pipes_1.fd[1]);
  return 0;
}