Re: [PATCH v13 01/11] cpuset: Enable cpuset controller in default hierarchy

[Tom Hromatka]

On 10/15/2018 12:41 PM, Waiman Long wrote:
> On 10/15/2018 02:31 PM, Tom Hromatka wrote:
> > On 10/12/2018 11:55 AM, Waiman Long wrote:
> > > Given the fact that thread mode had been merged into 4.14, it is now
> > > time to enable cpuset to be used in the default hierarchy (cgroup v2)
> > > as it is clearly threaded.
> > >
> > > The cpuset controller had experienced feature creep since its
> > > introduction more than a decade ago. Besides the core cpus and mems
> > > control files to limit cpus and memory nodes, there are a bunch of
> > > additional features that can be controlled from the userspace. Some of
> > > the features are of doubtful usefulness and may not be actively used.
> > >
> > > This patch enables cpuset controller in the default hierarchy with
> > > a minimal set of features, namely just the cpus and mems and their
> > > effective_* counterparts.  We can certainly add more features to the
> > > default hierarchy in the future if there is a real user need for them
> > > later on.
> > I really appreciate this simplification of the cpuset controller.
> >
> > I currently have an in-house customer that is unhappy with the
> > way cgroups cpuset v1 handles offlined CPUs.  This patchset makes two
> > significant improvements over current cpuset v1 behavior.  1) It allows
> > for offlined CPUs to be added to a cpuset (even though the CPU is
> > offline) and 2) it restores CPUs back to the requested cpuset when they
> > come back online.  This is more intuitive and secure for my customers.
> > Thank you!
> >
> > In part because of this patchset, I plan on proposing similar behavior
> > for offlined CPUs to cpuset v1.
> >
> > Thanks.
> >
> > Tom
> If you are just talking about the ability for cpuset to revert back to
> its original state when an offlined CPU becomes online again, that
> capability can be activated in v1 using the "cpuset_v2_mode" mount
> option when mounting the cpuset cgroup. However, that is not the default
> for v1.
>
> -Longman

Thanks!!! I didn't realize cpuset_v2_mode exists. (I see you
added it last year. Thank you!) I'll try it out and see if it
meets my customer's needs.

Tom