Re: [RFC 0/5] forced comounts for cgroups.

[Peter Zijlstra]

On Wed, 2012-09-05 at 13:12 +0400, Glauber Costa wrote:
> On 09/05/2012 01:11 PM, Tejun Heo wrote:
> > Hello, Peter.
> > 
> > On Wed, Sep 05, 2012 at 11:06:33AM +0200, Peter Zijlstra wrote:
> >> *confused* I always thought that was exactly what you meant with unified
> >> hierarchy.
> > 
> > No, I never counted out differing granularity.
> > 
> 
> Can you elaborate on which interface do you envision to make it work?
> They will clearly be mounted in the same hierarchy, or as said
> alternatively, comounted.
> 
> If you can turn them on/off on a per-subtree basis, which interface
> exactly do you propose for that?

I wouldn't, screw that. That would result in the exact same problem
we're trying to fix. I want a single hierarchy walk, that's expensive
enough.

> Would a pair of cgroup core files like available_controllers and
> current_controllers are a lot of drivers do, suffice?

No.. its not a 'feature' I care to support for 'my' controllers.

I simply don't want to have to do two (or more) hierarchy walks for
accounting on every schedule event, all that pointer chasing is stupidly
expensive.
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