Re: [PATCH v7 2/5] cpuset: Add cpuset.sched_load_balance to v2

Mike Galbraith
2018-05-02T14:35:48Z

On Wed, 2018-05-02 at 16:02 +0200, Peter Zijlstra wrote:
> On Wed, May 02, 2018 at 09:47:00AM -0400, Waiman Long wrote:
>
> > > I've read half of the next patch that adds the isolation thing. And
> > > while that kludges around the whole root cgorup is magic thing, it
> > > doesn't help if you move the above scenario on level down:
> > >
> > >
> > > R
> > > / \
> > > A B
> > > / \
> > > C D
> > >
> > >
> > > R: cpus=0-7, load_balance=0
> > > A: cpus=0-1, load_balance=1
> > > B: cpus=2-7, load_balance=0
> > > C: cpus=2-3, load_balance=1
> > > D: cpus=4-7, load_balance=1
> > >
> > >
> > > Also, I feel we should strive to have a minimal amount of tasks that
> > > cannot be moved out of the root group; the current set is far too large.
> >
> > What exactly is the use case you have in mind with loading balancing
> > disabled in B, but enabled in C and D? We would like to support some
> > sensible use cases, but not every possible combinations.
>
> Suppose A is your system group, and C and D are individual RT workloads
> or something.

Yeah, it does have a distinct "640K ought to be enough for anybody"
flavor to it.

-Mike