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

[Tejun Heo <tj@kernel.org>]

Hello, Peter.

On Tue, May 12, 2026 at 10:10:00AM +0200, Peter Zijlstra wrote:
...
> Anyway, this is why I've been looking at these alternative weight
> schemes, to get the nominal fraction near 1 and make these problems go
> away. It is both the numerical issues and the disparity between levels
> (with root being at level 0 being the most obvious).

I see. I think what bothers me is that I'm unsure what the weight config
would mean when the shares are scaled by the number of active cpus in that
cgroup. Here's a simple example:

- There are 256 cpus.
- /cgroup-A has weight 100 and 128 active threads. No pinning.
- /cgroup-B has weight 100 and 256 active thredas. No pinning.

In the current code, assuming math holds up, cgroup-A and B would get about
the same shares - ~128 CPUs each. However, if we scale the share by active
CPUs in each cgroup, B's tasks would end up with the same weight as A's on
CPUs that they end up competing on, which would lead to ~ 1:3 distribution.
Is that the right reading of the code?

Thanks.

-- 
tejun