The size of result from vfork() + pipe()

Dear all,

I am using vfork()+pipe() to excute a system command, for example "ifconfig LAN", and to get result by read the pipe. When my DRAM_SIZE is configured as 8MB, I can get a full size of result, such as

440bytes, but when my DRAM_SIZE is configured as 16MB, I can only get a incomplete result: 256bytes.

Can anyone tell me:

1. How to increase the size of pipe in uClinux?
2. Why does DRAM_SIZE incfluence the size of pipe?

My system configuration:

OS: uClinux Processor: ARM946-ES DRAM is 16MB

Thanks,

Kent Email: snipped-for-privacy@sjtu.org