Re: [PATCH v2 00/10] sched: Flatten the pick

[Qais Yousef]

On 05/11/26 13:31, Peter Zijlstra wrote:
> Hi!
> 
> So cgroup scheduling has always been a pain in the arse. The problems start
> with weight distribution and end with hierachical picks and it all sucks.

It does..

Not that it is useful info, but we talked briefly about it at OSPM, so thought
I'll report back. I gave this a go with my test case from schedqos announcement
[1] of running schbench with kernel build as BACKGROUND noise, but the fairness
imposed at group level is preserved (as expected) even if the pick is
flattened.

I do actually want a total flat system, ie: disable this whole thing :-)

The problem is to create a system where you want to introduce smart tagging
based on tasks, group scheduling becomes a big problem. If a task is set as
background or interactive, it has to be global to be enforced otherwise it
loses its meaning. And my test case stresses two long running tasks one is
interactive but the other is background and group scheduling imposes fairness
that breaks the task level tagging. Managing deadline via runtime doesn't help
here since they are both always busy tasks; and one must use nice values to
manage bandwidth. But nice values are local when autogroup/cgroups are present.

I need to find a simple way to turn this thing off at runtime and properly
flatten it ;-)

/runs away

[1] https://lore.kernel.org/lkml/20260415000910.2h5misvwc45bdumu@airbuntu/