memory allocation beyond 1GB datasize in linux emulation?

In article <871wuj2igm.wl%schutz_musp.ac.fj>,
Marko Schütz  <schutz_musp.ac.fj> wrote:
>-=-=-=-=-=-
>
>I want to allow the datasize of a linux binary to grow
up to 1800MB.
>
>As root I set the hard limit on datasize to 2048m, but
when I then su
>to my user account and check the hard limit I find it's
only 1024m. I
>tried defining a login class that has a datasize of
2048m and use 
>'su -c ...', but it didn't do it.
>
>I ended up running the binary as root. Watching 'top'
I saw it grow to
>a size of ~1047M and then it reported that memory
allocation failed.
>
>I'd be thankful for any hints on this...

Can you ktrace it and see which system call fails?

christos