Re: [ckrm-tech] [PATCH 00/10] Containers(V10): Generic Process Containers

[Serge E. Hallyn]

Quoting Paul Jackson (pj@xxxxxxx):
> > I suppose as a cleaner alternative we could 
> > add a container_subsys->inherit_defaults() handler, to be called at
> > container_clone(), and for cpusets this would set cpus and mems to
> > the parent values - sibling exclusive values.  If that comes to nothing,
> > then the attach_task() is still refused, and the unshare() or clone()
> > fails, but this time with good reason.
> 
> Unfortunately, I haven't spent the time I should thinking about
> container cloning, namespaces and such.
> 
> I don't know, for the workloads that matter to me, when, how or
> if this container cloning will be used.
> 
> I'm tempted to suggest the following.
> 
> First, I am assuming that the classic method of creating cpuset
> children will still work, such as the following (which can fail
> for certain combinations of exclusive cpus or mems):
> 	cd /dev/cpuset/foobar
> 	mkdir foochild
> 	cp cpus foochild
> 	cp mems foochild
> 	echo $$ > foochild/tasks
> 
> Second, given that, how about you fail the unshare() or clone()
> anytime that the instance to be cloned has any sibling cpusets
> with any exclusive flags set.

The below patch (on top of my previous patch) does basically that.  But
I wasn't able to test it, bc i wasn't able to set cpus_exclusive...

For /cpusets/set0/set1 to have cpu 1 exclusively, does /cpusets/set0
also have to have it exclusively?

If so, then clearly this approach won't work, since if any container has
exclusive cpus, then every container will have siblings with exclusive
cpus, and unshare still isn't possible on the system.

> The exclusive property is not really on friendly terms with cloning.
> 
> Now if the above classic code must be encoded using cloning under
> the covers, then we've got problems, probably more problems than
> just this.
> 
> -- 
>                   I won't rest till it's the best ...
>                   Programmer, Linux Scalability
>                   Paul Jackson <pj@xxxxxxx> 1.925.600.0401

thanks,
-serge