Re: [PATCHSET for-4.11] cgroup: implement cgroup v2 thread mode

[Peter Zijlstra]

On Thu, Feb 02, 2017 at 04:52:29PM -0500, Tejun Heo wrote:

> > Why do you need to manually turn it on?  That is, couldn't it be
> > automatic based on what controllers are enabled?
> 
> This came up already but it's not like some controllers are inherently
> thread-only.  Consider CPU, all in-context CPU cycle consumptions are
> tied to the thread; however, we also want to be able to account for
> CPU cycles consumed for, for example, memory reclaim or encryption
> during writeback.
> 
> I played with an interface where thread mode is enabled automatically
> upto the common ancestor of the threads but not only was it
> complicated to implement but also the eventual behavior was very
> confusing as the resource domain can change without any active actions
> from the user.  I think keeping things simple is the right choice
> here.

Note that the explicit marking of the resource domains gets you exactly
that. But let me reply in the other subthread.