On Thu, Jul 18, 2019 at 07:17:45PM +0100, Patrick Bellasi <patrick.bellasi@xxxxxxx> wrote: > The clamp values are not tunable at the level of the root task group. > That's for two main reasons: > > - the root group represents "system resources" which are always > entirely available from the cgroup standpoint. > > - when tuning/restricting "system resources" makes sense, tuning must > be done using a system wide API which should also be available when > control groups are not. > > When a system wide restriction is available, cgroups should be aware of > its value in order to know exactly how much "system resources" are > available for the subgroups. IIUC, the global default would apply in uclamp_eff_get(), so this propagation isn't strictly necessary in order to apply to tasks (that's how it works under !CONFIG_UCLAMP_TASK_GROUP). The reason is that effective value (which isn't exposed currently) in a group takes into account this global restriction, right? > @@ -1043,12 +1063,17 @@ int sysctl_sched_uclamp_handler(struct ctl_table *table, int write, > [...] > + if (update_root_tg) > + uclamp_update_root_tg(); > + > /* > * Updating all the RUNNABLE task is expensive, keep it simple and do > * just a lazy update at each next enqueue time. Since uclamp_update_root_tg() traverses down to uclamp_update_active_tasks() is this comment half true now?
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