Add support for Linux memory policy

[askervin]

Enable setting a NUMA memory policy for the container. New linux.mempolicy object contains inputs to the set_mempolicy(2) syscall.

[kad]

Small nit, I'd suggest to use MemoryPolicy and memoryPolicy instead of mempolicy. It would be more readable IMHO.

[giuseppe]

LGTM after the changes suggested above

[askervin]

Small nit, I'd suggest to use MemoryPolicy and memoryPolicy instead of mempolicy. It would be more readable IMHO.

Thanks @kad, fixed. Definitely better.

[utam0k]

It seems set_mempolicy(2) is only effective agains for called threads.

I'm not sure but we may need to implement it in nsexec.c of runc because of the thread limitation. I recommend to implement PoC in runc.

[giuseppe]

It seems set_mempolicy(2) is only effective agains for called threads. I'm not sure how to do it for processes created with exec. Any ideas?

the man page says:

The process memory policy is preserved across an [execve](https://linux.die.net/man/2/execve)(2), and is inherited by child processes created using [fork](https://linux.die.net/man/2/fork)(2) or [clone](https://linux.die.net/man/2/clone)(2).

so I don't think it is a problem for the spec

[utam0k]

@giuseppe Oh, I missed it. Looks good.