Messages in this thread | | | Subject | Re: [PATCH v3 12/14] sched/core: uclamp: add system default clamps | From | Dietmar Eggemann <> | Date | Mon, 20 Aug 2018 12:18:40 +0200 |
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On 08/06/2018 06:39 PM, Patrick Bellasi wrote: > Clamp values cannot be tuned at the root cgroup level. Moreover, because > of the delegation model requirements and how the parent clamps > propagation works, if we want to enable subgroups to set a non null > util.min, we need to be able to configure the root group util.min to the > allow the maximum utilization (SCHED_CAPACITY_SCALE = 1024).
Why 1024 (100)? Would any non 0 value work here?
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> @@ -1269,6 +1296,75 @@ static inline void uclamp_group_get(struct task_struct *p, > uclamp_group_put(clamp_id, prev_group_id); > } > > +int sched_uclamp_handler(struct ctl_table *table, int write, > + void __user *buffer, size_t *lenp, > + loff_t *ppos) > +{ > + int group_id[UCLAMP_CNT] = { UCLAMP_NOT_VALID }; > + struct uclamp_se *uc_se; > + int old_min, old_max; > + int result; > + > + mutex_lock(&uclamp_mutex); > + > + old_min = sysctl_sched_uclamp_util_min; > + old_max = sysctl_sched_uclamp_util_max; > + > + result = proc_dointvec(table, write, buffer, lenp, ppos); > + if (result) > + goto undo; > + if (!write) > + goto done; > + > + if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max) > + goto undo; > + if (sysctl_sched_uclamp_util_max > 1024) > + goto undo; > + > + /* Find a valid group_id for each required clamp value */ > + if (old_min != sysctl_sched_uclamp_util_min) { > + result = uclamp_group_find(UCLAMP_MIN, sysctl_sched_uclamp_util_min); > + if (result == -ENOSPC) { > + pr_err("Cannot allocate more than %d UTIL_MIN clamp groups\n", > + CONFIG_UCLAMP_GROUPS_COUNT); > + goto undo; > + } > + group_id[UCLAMP_MIN] = result; > + } > + if (old_max != sysctl_sched_uclamp_util_max) { > + result = uclamp_group_find(UCLAMP_MAX, sysctl_sched_uclamp_util_max); > + if (result == -ENOSPC) { > + pr_err("Cannot allocate more than %d UTIL_MAX clamp groups\n", > + CONFIG_UCLAMP_GROUPS_COUNT); > + goto undo; > + } > + group_id[UCLAMP_MAX] = result; > + } > + > + /* Update each required clamp group */ > + if (old_min != sysctl_sched_uclamp_util_min) { > + uc_se = &uclamp_default[UCLAMP_MIN]; > + uclamp_group_get(NULL, UCLAMP_MIN, group_id[UCLAMP_MIN], > + uc_se, sysctl_sched_uclamp_util_min); > + } > + if (old_max != sysctl_sched_uclamp_util_max) { > + uc_se = &uclamp_default[UCLAMP_MAX]; > + uclamp_group_get(NULL, UCLAMP_MAX, group_id[UCLAMP_MAX], > + uc_se, sysctl_sched_uclamp_util_max); > + } > + > + if (result) { > +undo: > + sysctl_sched_uclamp_util_min = old_min; > + sysctl_sched_uclamp_util_max = old_max; > + }
This looks strange! In case uclamp_group_find() returns free_group_id instead of -ENOSPC, the sysctl min/max values are reset?
I was under the assumption that I could specify:
sysctl_sched_uclamp_util_min = 40 (for boosting) sysctl_sched_uclamp_util_max = 80 (for clamping)
with an empty cpu controller hierarchy and then those values become the .effective values of (a first level) task group?
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