Problem with OOM killer killing process even when there is plenty of RAM.

Hi, I am trying to allocate 512MB of RAM in my driver loaded as a module, but the OOM killer starts killing all my processes. This machine has around 24GB RAM and is a 8 core Xeon. The RAM is allocated in page size chunks (i.e. 131072 chunks each of size PAGE_SIZE). I am using a 32 bit kernel with PAE enabled. The allocation works fine on a machine with 8GB of RAM. Thanks.