The following code is supposed to make 100,000 threads:
/* compile with: gcc -lpthread -o thread-limit thread-limit.c */
/* originally from: http://www.volano.com/linuxnotes.html */
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#define MAX_THREADS 100000
int i;
void run(void) {
sleep(60 * 60);
}
int main(int argc, char *argv[]) {
int rc = 0;
pthread_t thread[MAX_THREADS];
printf("Creating threads ...\n");
for (i = 0; i < MAX_THREADS && rc == 0; i++) {
rc = pthread_create(&(thread[i]), NULL, (void *) &run, NULL);
if (rc == 0) {
pthread_detach(thread[i]);
if ((i + 1) % 100 == 0)
printf("%i threads so far ...\n", i + 1);
}
else
{
printf("Failed with return code %i creating thread %i (%s).\n",
rc, i + 1, strerror(rc));
// can we allocate memory?
char *block = NULL;
block = malloc(65545);
if(block == NULL)
printf("Malloc failed too :( \n");
else
printf("Malloc worked, hmmm\n");
}
}
sleep(60*60); // ctrl+c to exit; makes it easier to see mem use
exit(0);
}
This is running on a 64bit machine with 32GB of RAM; Debian 5.0 installed, all stock.
- ulimit -s 512 to keep the stack size down
- /proc/sys/kernel/pid_max set to 1,000,000 (by default, it caps out at 32k pids).
- ulimit -u 1000000 to increase max processes (don't think this matters at all)
- /proc/sys/kernel/threads-max set to 1,000,000 (by default, it wasn't set at all)
Running this spits out the following:
65500 threads so far ...
Failed with return code 12 creating thread 65529 (Cannot allocate memory).
Malloc worked, hmmm
I'm certainly not running out of ram; I can even launch several more of these programs all running at the same time and they all start their 65k threads.
(Please refrain from suggesting I not try to launch 100,000+ threads. This is simple testing of something which should work. My current epoll-based server has roughly 200k+ connections at all times and various papers would suggest that threads just might be a better option. - Thanks :) )