From: Michael Buesch <mb@bu3sch.de>
To: Robert Hancock <hancockr@shaw.ca>
Subject: Re: Maximum number of processes in Linux
Date: Wed, 16 Aug 2006 01:39:16 +0200
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Cc: linux-kernel@vger.kernel.org, Irfan Habib <irfan.habib@gmail.com>
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On Wednesday 16 August 2006 01:12, Robert Hancock wrote:
> Irfan Habib wrote:
> > Hi,
> > 
> > What is the maximum number of process which can run simultaneously in
> > linux? I need to create an application which requires 40,000 threads.
> > I was testing with far fewer numbers than that, I was getting
> > exceptions in pthread_create
> 
> What architecture is this? On a 32-bit architecture with a 2MB stack 
> size (which I think is the default) you couldn't possibly create more 
> than 2048 threads just because of stack space requirements. Reducing the 
> stack size would get you more.

Hm, I'm on a 4way PPC64 machine with 2.5G RAM.
It can only create 509 pthreads and fails with ENOMEM
on the 510th.
That's not a really big machine, but I expected it to be able
to create somewhere around 8000 threads or so, at least. Especially
as it has a 64bit kernel and lots of memory.

Well...

That's my test app:

#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <errno.h>


static void * thread(void *arg)
{
        while (1)
                sleep(10);
}

int main(void)
{
        int err = 0;
        unsigned long i = 0;
        pthread_t t;

        while (!err) {
                err = pthread_create(&t, NULL, thread, NULL);
                i++;
                if (err) {
                        printf("Creating pthread %lu failed with \"%s\"\n",
                                i, strerror(errno));
                        break;
                }
                printf("%lu pthreads created\n", i);
        }

        return 0;
}

-- 
Greetings Michael.
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