calc.rb

#!/usr/bin/env ruby

def read_file(filename)
    ret = []
    File.open(filename) do |f|
        f.each_line do |line|
            ret << line.split(',')[1].to_i
        end
    end
    return ret

end

if __FILE__ == $0
    if ARGV.length == 0
        puts("usage: #{$0} file")
        exit(-1)
    end

    data = read_file(ARGV[0])

    average = data.inject(0.0) { |r, i| r += i } / data.size
    mid = data.size % 2 == 0 ? data[data.size / 2 - 1, 2].inject(:+) / 2.0 : data[data.size / 2]
    
    puts("Average, Median")
    puts("#{average},#{mid}")

end

pidns_tester.c

#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

static inline unsigned long rdtsc(void)
{
	unsigned long a, d;
	__asm__ volatile("rdtsc" : "=a"(a), "=d"(d));
	return (d << 32) | a;
}

static int create_shered_memory(int num_test)
{
	int ret = 0;
	size_t size = num_test * 16; // keep 16 bytes for one line
	ret = shmget(IPC_PRIVATE, size, 0666);
	if (ret < 0) {
		perror("semget");
		exit(-1);
	}
	return ret;
}

static inline void *do_shmat(int shmid)
{
	void *addr = shmat(shmid, NULL, 0);
	if (addr < 0) {
		perror("shmat");
		exit(-1);
	}
	return addr;
}

static inline void do_shmdt(void *addr)
{
	if (shmdt(addr) < 0) {
		perror("shmdt");
		exit(-1);
	}
}
int main(int argc, char **argv)
{
	unsigned long i, max = 1000;
	unsigned long after, before;
	char buf[64] = {0};
	int shmid;
	char *shmaddr;

	if (argc > 1)
		max = strtoul(argv[1], NULL, 10);

	shmid = create_shered_memory(max);

	for (i = 0; i < max; i++) {
		pid_t pid = fork();
		if (!pid) { // child
			before = rdtsc();
			syscall(SYS_getpid);
			after = rdtsc();
			sprintf(buf, "%lu,%lu\n", i, after - before);
			shmaddr = do_shmat(shmid);
			strcat(shmaddr, buf);
			do_shmdt(shmaddr);
			_exit(0);
		} else if (pid > 0) { // parent
			waitpid(pid, NULL, 0);
	        } else {
			perror("fork()");
			exit(-1);
		}
	}

	shmaddr = do_shmat(shmid);
	printf("%s\n", shmaddr);
	do_shmdt(shmaddr);


}

run-calc.sh

#!/bin/bash

if [ $# -ne 1 ]; then
    echo "usage: ${0} name"
    exit 1
fi

name=$1

for ((i = 0; i < 5; i++));
do
    ./calc.rb ${name}_${i}.txt
done

run-test.sh

#!/bin/bash

if [ $# -ne 1 ]; then
    echo "usage: ${0} name"
    exit 1
fi

name=$1

for ((i = 0; i < 5; i++));
do
    echo "run test ${i}"
    ./pidns_tester 100000 > ${name}_${i}.txt
done