Re: I can't create thread more than 256 on Redhat 9

From: Waldek Hebisch (hebisch_at_math.uni.wroc.pl)
Date: 01/07/04 

Date: 7 Jan 2004 14:42:21 GMT

Kihong Lee (sisapinusa@yahoo.com) wrote:
: hebisch@math.uni.wroc.pl (Waldek Hebisch) wrote in message news:<btej3d$jaj$1@panorama.wcss.wroc.pl>...
: > It looks that each thread takes 8MB of virtual memory for the stack.
: > So IMHO you are running out of virtual memory. So either set lower
: > limit on treads stack size (I do not know how, but that is a standard
: > parameter) or get 64-bit machine.

: You mean, I might have to modify kernel header file to adjust stack
: size, and do kernel complie again, right?

No, it is a parameter in the thread library. On RedHat 9 (nptl) the following
program went up to 4091 threads (on 512 MB machine):

/* compile with: gcc -lpthread -o thread-limit thread-limit.c */
/* originally from: http://www.volano.com/linuxnotes.html */

#include <stdio.h>
#include <unistd.h>
#include <pthread.h>

#define MAX_THREADS 10000
int i;

void run(void) {
  char c;
  if (i < 10)
    printf("Address of c = %u KB\n", (unsigned int) &c / 1024);
  sleep(60 * 60);
}

int main(int argc, char *argv[]) {
  int rc = 0;
  pthread_t thread[MAX_THREADS];
  pthread_attr_t attribites;
  pthread_attr_init(&attribites);
  /* Set low stack limit to allow more threads */
  pthread_attr_setstacksize (&attribites, 64*1024);
  printf("Creating threads ...\n");
  for (i = 0; i < MAX_THREADS && rc == 0; i++) {
    rc = pthread_create(&(thread[i]), &attribites, (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.\n",
             rc, i + 1);
  }
  exit(0);
}

It seems that earlier threads libraries (linuxthreads) may ignore
stack settings, then you would be forced to recompile `linuxthreads'
(probably the whole glibc). 

--
                              Waldek Hebisch
hebisch@math.uni.wroc.pl

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