Re: [RFC] [PATCH 00/13] Introduce task_pid api

[Hubertus Franke]

Serge E. Hallyn wrote:
> Quoting Paul Jackson (pj@xxxxxxx):
>
> > An additional per-task attribute, set by a batch manager typically
> > when it starts a job on a checkpointable, restartable, movable
> > "virtual server" connects the job parent task, and hence all its
> > descendents in that job, with a named kernel object that has among its
> > attributes a pid range.  When fork is handing out new pids, it honors
> > that pid range.  User level code, in the batch manager or system
> > administration layer manages a set of these named virtual servers,
> > including assigning pid ranges to them, and puts what is usually the
> > same such configuration on each server in the farm.

And that's how we implement this.
The difference is that the pidrange-id is assigned on the fly,
that is when the virtual server is created or recreated after restart.

This, as described in my previous note, is more scalable, because I don't have
to do a global pidrange partitioning.
global pidrange partitioning has implications, for instance what if I simply
want to freeze an app only to restart it much later. This would freeze that
range autmatically.

On process restart, we force fork to use a particular <pidspace/pid> for its
kernel pid assignment, rather then searching for a free one.

-- Hubertus



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