Re: RFC [patch 13/34] PID Virtualization Define new task_pid api

[Kirill Korotaev <dev@sw.ru>]

> > How can you migrate application which consists of two processes doing 
> > IPC via signals? They are not tired inside kernel anyhow and there is
> > no way to automatically detect that both should be migrated together.
> > VPSs what provides you such kind of boundaries of what should be 
> > considered as a whole.
>
>
> Could you explain a little bit _how_ VPSs provide this?
OpenVZ virtualizes kernel resources such as IPC making them per-VPS. 
Processes in VPS deal with such virtualized resources, so they 
efficiently should be migrated together. That's it - a whole container 
with its resources should be considered as a whole.

Signals are not virtualized in this manner since they are rather 
per-task resource, but OpenVZ introduces strict boundaries in kernel 
which make sure that no any 3rd task from another container (VPS) will 
be participating in the communication.

Kirill

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