Re: [PATCH v12 3/6] sched/core: uclamp: Propagate system defaults to root group
From: Michal Koutný <mkoutny@suse.com>
Date: 2019-07-25 11:41:49
Also in:
cgroups, linux-pm, lkml
On Thu, Jul 18, 2019 at 07:17:45PM +0100, Patrick Bellasi [off-list ref] 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?
quoted hunk ↗ jump to hunk
@@ -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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