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Message-ID: <fc67f8b70505131753103d2dc7@mail.gmail.com>
Date: Fri, 13 May 2005 20:53:11 -0400
From: Ritesh Kumar <digitalove@gmail.com>
Reply-To: ritesh@cs.unc.edu
To: Jakub Jelinek <jakub@redhat.com>
Subject: Re: NPTL: stack limit limiting number of threads
Cc: Linux Kernel Development <linux-kernel@vger.kernel.org>
In-Reply-To: <20050514000643.GI17420@devserv.devel.redhat.com>
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On 5/13/05, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, May 13, 2005 at 08:02:48PM -0400, Ritesh Kumar wrote:
> >     Thanks for your reply. I actually went ahead after getting your
> > mail and coded up a small program to check the stack limit
> > deliberately. The program is shown inline.
> >
> > #include <stdio.h>
> >
> > #define BUF_SIZE 1024000
> >
> > void recurse(int n){
> >       char ch[BUF_SIZE];
> >       if(n<=0)
> >               return;
> >       else
> >               recurse(n-1);
> > }
> >
> > int main(argc, argv)
> >       int argc;
> >       char **argv;
> > {
> >       if(argc!=2){
> >               printf("Usage: %s <n (megabytes)>\n", argv[0]);
> >               return 1;
> >       }
> >       printf("Checking for %dMB\n", atoi(argv[1]));
> >       recurse(atoi(argv[1]));
> > }
> >
> > Its a fairly crude way to find out the actual stack limit. Basically,
> > the resurse function recurses each time allocating ~1MB of space on
> > the stack. The program segfaults exactly at the ulimit -s value of
> > stack size on both linux and freebsd. So it does seem that the ulimit
> > -s is the value of stack limit used on FreeBSD.
> 
> For the main stack sure.  But now try to call that recurse in
> some other thread.
> 
>         Jakub
> 

Oh great... I see your point now. I called the same recurse in an
alternative thread and found the limit to be 8M on Linux ( and Mac OS
X (Panther)) but around 1MB on FreeBSD. Thanks for the clarification!

Ritesh 

-- 
http://www.cs.unc.edu/~ritesh/
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