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SubjectRe: malloc problem to allocate very large blocks
I missed the system details, you already have >2GB virtual memory.

--tomar
On Tue, 29 Jul 2003, Tomar, Nagendra wrote:

> AFAIK malloc will not return you memory more than the total virtual
> memory
> (RAM+swap) in the system. So if you want more than 2GB allocations from
> malloc, make sure you have at least 2GB virtual mem, keeping aside some
> space for the kernel.
>
> --tomar
>
> On Mon, 28 Jul 2003, Tung-Han Hsieh wrote:
>
> > 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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