HELP

Jakob Østergaard jakob at unthought.net
Sat Aug 25 16:38:07 EDT 2001


On Tue, Aug 14, 2001 at 04:26:54PM +0100, J. M. Pacheco wrote:
> 
> 	Hello.
> 
...
> Can anyone help me out of this mess ? 
> Furthermore, browsing the beowulf mailing list, I got accross some linux
> limitations in writing huge temperary files. Mine can be 2 GB large. Is
> that problem solved in kernels 2.4 ? 

The problem resided both in the kernel and standard libraries, so either
updating glibc *or* updating the kernel won't solve the problem.

However, newer distributions such as RedHat 7.1 have both glibc and kernel
updated so that this is no longer a problem.

I would think your distribution had this solved too - but I do not know.

The last problem in writing 2+ GB files, is the application (and it's libraries
including any compiler-included support libraries).   If you have code that
uses a 32-bit signed integer for byte-offsets into your file, well, naturally
you cannot address more than 2 GB no matter which kernel you're running.

If (and this is *pure* speculation!) g77 generated Fortran code relies on
a support library for file I/O that uses such addressing, this could be the
explanation for the problems you see.

Test:  Try dd if=/dev/zero of=test_file bs=8k count=1024k

If you end up with a test_file of size 8 GB, your kernel, glibc, and tools
(well, dd at least) have proper LFS support.  The problem must then be with
your code or g77 (or support libraries).

If you do not end up with the large file, I suggest you try another
distribution that has proper kernel and libraries.   Or, see if there are
updates to your distribution that fix this.

-- 
................................................................
:   jakob at unthought.net   : And I see the elder races,         :
:.........................: putrid forms of man                :
:   Jakob Østergaard      : See him rise and claim the earth,  :
:        OZ9ABN           : his downfall is at hand.           :
:.........................:............{Konkhra}...............:

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