memory size in tz_vmm

[lzSun]

Hello,
I am very interested in genode and I am working on tz_vmm demo using i.mx53-qsb board now. After the tz_vmm start,  I find a boot message like this:
" Genode 18.05 <local changes>
211 MiB RAM and 64535 caps assigned to init "

To my understanding, it's present that the available memory that the genode os in secure world is 211MB. And After the system boot up, I use Top command to observe the memroy that normal world have which gives me like this:
" Mem: 37956K used, 49444K free, 0K shrd, 68K buff, 26456K cached "

This shows that the total memory the linux in the normal world can use is less than 150MB. And I have some questions about this:
1. Can this memory size be increased? For example, I want to increase the memory size that genode can use. To my understanding, this memory distribution between two worlds(secure and normal) can be configured. So I wonder whether I can determine 
this memory distribution. If it's indeed configurable,  where I can find the source file to configure this and whether this configuration can be changed dynamically when the system is running. 
2. As far as I know, the i.mx53-qsb have 1GB, but from the situation above, the total memory size is about 400MB which is far less than 1GB. So why can this situation happened?
Thanks,
Best wishes
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