Memory Resource in SDRAM

Hello, my question is the following:
  I have created an application created in SDRAM in which I do
"xil_malloc(16*4096)". The problem is that it seems like there is not
memory sufficient for my application. I have increased "HEAP_SIZE" and
"STACK_SIZE" but I suppose that these parameters are not the problem.
My sdram is 32Mb so I think I have enough memory for this
requeriments. What can I do? How can I increase the memory for an
app?. I use Xilkernel.

Thanks for your help