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SubjectRe: 2.4.4 sluggish under fork load
From
Date
John Kacur <jkacur@home.com> writes:

> >Peter Osterlund wrote:
> >>
> >> Another thing is that the bash loop "while true ; do /bin/true ; done" is
> >> not possible to interrupt with ctrl-c.
>
> > Same thing here.
>
> I'm not having any problems. Just a quick question, is everyone who is
> having a problem running with more than one cpu?

A clarification. The bash loop above doesn't cause any sluggishness on
my single cpu system. The non-working ctrl-c is probably just a bash
bug. The child process must eat some cpu time to provoke the
sluggishness, like in the following test program where the child busy
waits 100ms and then exits:

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>

int main(int argc, char* argv[])
{
double childTime = 0.10;
if (argc > 1)
childTime = atof(argv[1]);

for (;;) {
int child = fork();
if (child == -1) {
printf("fork error\n");
exit(0);
} else if (child > 0) {
while (waitpid(child, NULL, 0) != child)
;
printf("."); fflush(stdout);
} else {
struct timeval tv1, tv2;
double t;
gettimeofday(&tv1, NULL);
for (;;) {
gettimeofday(&tv2, NULL);
t = (tv2.tv_sec - tv1.tv_sec) +
(tv2.tv_usec - tv1.tv_usec) / 1000000.0;
if (t > childTime)
break;
}
_exit(0);
}
}

return 0;
}

--
Peter Österlund peter.osterlund@mailbox.swipnet.se
Sköndalsvägen 35 http://home1.swipnet.se/~w-15919
S-128 66 Sköndal +46 8 942647
Sweden

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