Re: [RFC v3 1/5] sched/core: add capacity constraints to CPU controller

[Tejun Heo <tj@kernel.org>]

On Mon, Mar 20, 2017 at 01:15:11PM -0400, Tejun Heo wrote:
> > a) are tunable at all hierarchy levels, i.e. root group too
> 
> This usually is problematic because there should be a non-cgroup way
> of configuring the feature in case cgroup isn't configured or used,
> and it becomes awkward to have two separate mechanisms configuring the
> same thing.  Maybe the feature is cgroup specific enough that it makes
> sense here but this needs more explanation / justification.

A related issue here is that what the non-cgroup interface and its
interaction with cgroup should be.  In the long term, I think it's
better to have a generic non-cgroup interface for these new features,
and we've gotten it wrong, or at least inconsistent, across different
settings - most don't affect API accessible settings and just confine
the configuration requested by the application inside the cgroup
constraints; however, cpuset does it the other way and overwrites
configurations set by individual applications.

If we agree that exposing this only through cgroup is fine, this isn't
a concern, but, given that this is a thread property and can obviously
be useful outside cgroups, that seems debatable at the very least.

Thanks.

-- 
tejun