Why application request RAM quota from parent even if it is enough?

[Alexander Tormasov]

> As long as "they" do not want to reserve (512 << 20) KiB there must be
> some miscalculation.

Unfortunately, they do want, as explicitly written in the comment -they even try to claim 544gb mem space initially... not real alloc, just reserve .

> 
>> Anyway, system should not hang even if I request 512gb of ram, it
>> should return with error...
>> This is standard approach - we try to alloc until we can, receiving
>> ENOMEM or something similar?
>> Why it is not working?
> 
> The current mmap(MAP_ANONYMOUS) implementation seems to strive for
> satisfaction of the application by not probing the allocation but
> enforcing it. This ends up in the request for more RAM resources as
> you traced.

Yes, but why this call (wait for response from parent) just hangs forever instead of return and say that “I can’t”?