From: Tung-Han Hsieh <thhsieh@xcin.phys.ntu.edu.tw>
Date: Mon, 28 Jul 2003 14:44:28 +0800
To: linux-kernel@vger.kernel.org
Cc: jamagallon@able.es
Subject: malloc problem to allocate very large blocks
Message-ID: <20030728064428.GA32138@xcin>
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Hello,

I am developing applications which requires more than 2GB memory.
But I found that in my Linux system the malloc() cannot allocate
more than 2GB memory. Here is the details of my system:

CPU:    Pentium 4 2.53 GHz
RAM:    2 GB
Swap:   512 MB
OS:	Debian-3.0 stable
Kernel: 2.4.20
gcc:	2.95.4 20011002
glibc:  2.2.5-6

In theory, in a 32-bits machine the maximum allocatable memory
is up to 4GB. But in the following very simple testing program:

=====================================================================
#include <stdio.h>
#include <stdlib.h>

main()
{
    size_t l;
    char *s1=NULL, *s2=NULL;

    l = 1024*1024*1024;

    s1 = malloc(l);
    s2 = malloc(l);
    if (! s1) printf("s1 malloc failed\n");
    if (! s2) printf("s2 malloc failed\n");
}
=====================================================================

only the block for s1 can be allocated. Further, if I change the
program to

=====================================================================
#include <stdio.h>
#include <stdlib.h>

main()
{
    size_t l;
    char *s1=NULL;

    l = 2*1024*1024*1024;

    s1 = malloc(l);
    if (! s1) printf("s1 malloc failed\n");
}
=====================================================================

the gcc complier complain to me that "foo.c:9: warning: integer overflow
in expression" during the compilation (I use: "gcc foo.c" to compile it),
and the block for s1 cannot be allocated at all. I am wondering if there
is any way to overcome the 2GB limit.

Thank you very much for your reply in advance.


Best Regards,

T.H.Hsieh
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