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SubjectRe: Definition of fairness (was Re: [patch] CFS scheduler, -v11)
On Wed, May 09, 2007 at 09:24:17PM +0200, Dmitry Adamushko wrote:
> One quick observation.
>
> Isn't it important for both processes to have the same "loops_per_ms" value?

Good catch.

I have modified the testcase based on this observation (using
setitimer).

--
Regards,
vatsa
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <sys/time.h>
#include <sys/resource.h>

volatile int time_elapsed;
int run_length = 52; // in milliseconds
int sleep_length = 24; // in milliseconds
int epoch_time = 5; // in seconds

void alrm_handler(int signo)
{
time_elapsed = 1;
}

main(int argc, char *argv[])
{
double prevusage = 0;
struct itimerval timer;
time_t prevtime;

if (argc > 1) {
run_length = atoi(argv[1]);
if (argc > 2)
sleep_length = atoi(argv[2]);
if (argc > 3)
epoch_time = atoi(argv[3]);
}

signal(SIGVTALRM, alrm_handler);
memset(&timer, 0, sizeof(timer));

timer.it_value.tv_sec = run_length / 1000;
timer.it_value.tv_usec = (run_length % 1000) * 1000;

printf ("run time = %d ms (%d sec + %d usec), sleep time = %d ms,"
" epoch time = %d s\n", run_length, timer.it_value.tv_sec,
timer.it_value.tv_usec, sleep_length, epoch_time);

prevtime = time(NULL);
while (1) {
time_t curtime, deltatime;
struct rusage stats;
int rc;

rc = setitimer(ITIMER_VIRTUAL, &timer, NULL);
if (rc < 0) {
perror("setitimer");
exit(1);
}

time_elapsed = 0;
while (!time_elapsed)
;

usleep(sleep_length * 1000);

curtime = time(NULL);
deltatime = curtime - prevtime;
if (deltatime >= epoch_time) {
double curusage, deltausage;

getrusage(0, &stats);
curusage = stats.ru_utime.tv_sec +
stats.ru_utime.tv_usec * 1e-6 +
stats.ru_stime.tv_sec +
stats.ru_stime.tv_usec * 1e-6;

deltausage = curusage - prevusage;
printf ("Obtained %3.2f seconds of execution time in"
" %d elapsed seconds \n", deltausage, deltatime);
prevtime = curtime;
prevusage = curusage;
}
}
}
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