Re: [PATCH v2] docs/sched_ext: document that cgroup CPU knobs are scheduler-dependent
Tejun Heo <[email protected]>
| Newsgroups | dev.linux.lists.sched-ext,org.kernel.vger.bpf,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
Hello, On Wed, Aug 19, 2026 at 09:21:57AM +0800, Tao Cui wrote: ... > +The fair class enforces cpu controller knobs such as ``cpu.max``, > +``cpu.weight`` and ``cpu.idle`` in the kernel. sched_ext only passes > +them to the BPF scheduler through ``ops.cgroup_set_weight()``, > +``ops.cgroup_set_idle()``, ``ops.cgroup_set_bandwidth()`` and friends. > +Whether and how a knob takes effect is up to the loaded scheduler: if > +it doesn't implement the corresponding callback, the knob is ignored. > +For example, none of scx_simple, scx_flatcg and scx_central implements > +``ops.cgroup_set_bandwidth()``, so with them ``cpu.max`` has no effect > +-- the cgroup runs at unlimited CPU with ``nr_throttled`` staying > +at 0. SCX doesn't have nr_throttled routing right now even for scheds that implement cpu.max (scx_lavd is the only one right now AFAIK). I'd keep the documentation more concise and generic. I don't think listing schedulers that don't implement the feature or specifically pointing to nr_throttled is all that useful given that most schedulers don't implement it right now. Thanks. -- tejun