从Python调用java时，分配超过4 GB的堆空间的问题

I am using using os.system call from python to run jar file. The jar file requires large heap space and thus i am allocating 4 Gb heap space using Xmx. When i execute the command "java -Xms4096m -Xmx4096m -jar camXnet.jar net.txt" from command line it executes properly, however when i call it from a python program via os.system, it works only if memory allocated is less than 4Gb, otherwise it fails to execute. Any solutions?I am using using os.system call from python to