On 03/19/2018 04:49 PM, Mike Galbraith wrote:

On Mon, 2018-03-19 at 08:34 -0700, Tejun Heo wrote:

quoted

Hello, Mike.

On Thu, Mar 15, 2018 at 03:49:01AM +0100, Mike Galbraith wrote:

quoted

Under the hood v2 details are entirely up to you.  My input ends at
please don't leave dynamic partitioning standing at the dock when v2
sails.

So, this isn't about implementation details but about what the
interface achieves - ie, what's the actual function?  The only thing I
can see is blocking the entity which is configuring the hierarchy from
making certain configs.  While that might be useful in some specific
use cases, it seems to miss the bar for becoming its own kernel
feature.  After all, nothing prevents the same entity from clearing
the exlusive bit and making the said changes.

Yes, privileged contexts can maliciously or stupidly step all over one
other no matter what you do (finite resource), but oxymoron creation
(CPUs simultaneously balanced and isolated) should be handled.  If one
context can allocate a set overlapping a set another context intends to
or already has detached from scheduler domains, both are screwed.

	-Mike

The allocations of CPUs to child cgroups should be controlled by the
parent cgroup. It is the parent's fault if some CPUs are in both
balanced and isolated cgroups.

How about we don't allow turning off scheduling if the CPUs aren't
exclusive from the parent's perspective? So you can't create an isolated
cgroup if the CPUs aren't exclusive. Will this be a good enough compromise?

Cheers,
Longman