Very Computer

Is there a limit on the total memory of all the processes in a
group?   My program forks off 4 subprocesses.   When their total
memory gets over about 4GB, then the last one goes into D state
forever.

My machine is a dual 2.4GHz Xeon with a motherboard capable of
12GB of real memory.  It has 4GB of real memory and 6GB more of
swap. It's running SuSE 8.1 on linux 2.4.19-64GB-SMP.

Thanks.