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SubjectRe: CFS review
Hi,

On Wed, 1 Aug 2007, Ingo Molnar wrote:

> Please also send me the output of this script:
>
> http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

Send privately.

> Could you also please send the source code for the "l.c" and "lt.c" apps
> you used for your testing so i can have a look. Thanks!

l.c is a simple busy loop (well, with the option to start many of them).
This is lt.c, what it does is to run a bit less than a jiffie, so it
needs a low resolution clock to trigger the problem:

#include <stdio.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>

#define NSEC 1000000000
#define USEC 1000000

#define PERIOD (NSEC/1000)

int i;

void worker(int sig)
{
struct timeval tv;
long long t0, t;

gettimeofday(&tv, 0);
//printf("%u,%lu\n", i, tv.tv_usec);
t0 = (long long)tv.tv_sec * 1000000 + tv.tv_usec + PERIOD / 1000 - 50;
do {
gettimeofday(&tv, 0);
t = (long long)tv.tv_sec * 1000000 + tv.tv_usec;
} while (t < t0);

}

int main(int ac, char **av)
{
int cnt;
timer_t timer;
struct itimerspec its;
struct sigaction sa;

cnt = i = atoi(av[1]);

sa.sa_handler = worker;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);

sigaction(SIGALRM, &sa, 0);

clock_gettime(CLOCK_MONOTONIC, &its.it_value);
its.it_interval.tv_sec = 0;
its.it_interval.tv_nsec = PERIOD * cnt;

while (--i > 0 && fork() > 0)
;

its.it_value.tv_nsec += i * PERIOD;
if (its.it_value.tv_nsec > NSEC) {
its.it_value.tv_sec++;
its.it_value.tv_nsec -= NSEC;
}

timer_create(CLOCK_MONOTONIC, 0, &timer);
timer_settime(timer, TIMER_ABSTIME, &its, 0);

printf("%u,%lu\n", i, its.it_interval.tv_nsec);

while (1)
pause();
return 0;
}

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