Check maxmem taking into account the minimum init memory that allows
that requested maximum memory.
Explanation:
Linux kernel needs space for memory-related structures created at boot.
If init_mem is just 400MB, then max_mem can't balloon above 4.3GB (at
which poing it yields "add_memory() failed: -17" messages and apps
crash), regardless of the max_mem_size value.
Based on Marek's findings and my tests on a 16GB PC, using several
processes like:
stress -m 1 --vm-bytes 1g --vm-hang 100
result in the following points:
init_mem ==> actual max memory
400 4300
700 7554
800 8635
1024 11051
1200 12954
1300 14038
1500 14045 <== probably capped on my 16GB system
The actual ratio of max_mem_size/init_mem is surprisingly constant at
10.79
If less init memory is set than that ratio allows, then the set
maxmem is unreachable and the VM becomes unstable (app crashes)
Based on qubes-devel discussion titled "Qubes Dom0 init memory against
Xen best practices?" at:
https://groups.google.com/d/msg/qubes-devel/VRqkFj1IOtA/UgMgnwfxVSIJ
bf2173073b