Commit 1a00d999971c78ab024a17b0efc37d78404dd120
Committed by
Ingo Molnar
Ingo Molnar
1 parent
a87498ace5
sched/uclamp: Set default clamps for RT tasks
By default FAIR tasks start without clamps, i.e. neither boosted nor
capped, and they run at the best frequency matching their utilization
demand. This default behavior does not fit RT tasks which instead are
expected to run at the maximum available frequency, if not otherwise
required by explicitly capping them.
Enforce the correct behavior for RT tasks by setting util_min to max
whenever:
1. the task is switched to the RT class and it does not already have a
user-defined clamp value assigned.
2. an RT task is forked from a parent with RESET_ON_FORK set.
NOTE: utilization clamp values are cross scheduling class attributes and
thus they are never changed/reset once a value has been explicitly
defined from user-space.
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alessio Balsini <balsini@android.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Steve Muckle <smuckle@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@google.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lkml.kernel.org/r/20190621084217.8167-9-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Showing 1 changed file with 28 additions and 2 deletions Side-by-side Diff
kernel/sched/core.c
| ... | ... | @@ -1062,6 +1062,27 @@ |
| 1062 | 1062 | static void __setscheduler_uclamp(struct task_struct *p, |
| 1063 | 1063 | const struct sched_attr *attr) |
| 1064 | 1064 | { |
| 1065 | + unsigned int clamp_id; | |
| 1066 | + | |
| 1067 | + /* | |
| 1068 | + * On scheduling class change, reset to default clamps for tasks | |
| 1069 | + * without a task-specific value. | |
| 1070 | + */ | |
| 1071 | + for_each_clamp_id(clamp_id) { | |
| 1072 | + struct uclamp_se *uc_se = &p->uclamp_req[clamp_id]; | |
| 1073 | + unsigned int clamp_value = uclamp_none(clamp_id); | |
| 1074 | + | |
| 1075 | + /* Keep using defined clamps across class changes */ | |
| 1076 | + if (uc_se->user_defined) | |
| 1077 | + continue; | |
| 1078 | + | |
| 1079 | + /* By default, RT tasks always get 100% boost */ | |
| 1080 | + if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) | |
| 1081 | + clamp_value = uclamp_none(UCLAMP_MAX); | |
| 1082 | + | |
| 1083 | + uclamp_se_set(uc_se, clamp_value, false); | |
| 1084 | + } | |
| 1085 | + | |
| 1065 | 1086 | if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) |
| 1066 | 1087 | return; |
| 1067 | 1088 | |
| ... | ... | @@ -1087,8 +1108,13 @@ |
| 1087 | 1108 | return; |
| 1088 | 1109 | |
| 1089 | 1110 | for_each_clamp_id(clamp_id) { |
| 1090 | - uclamp_se_set(&p->uclamp_req[clamp_id], | |
| 1091 | - uclamp_none(clamp_id), false); | |
| 1111 | + unsigned int clamp_value = uclamp_none(clamp_id); | |
| 1112 | + | |
| 1113 | + /* By default, RT tasks always get 100% boost */ | |
| 1114 | + if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) | |
| 1115 | + clamp_value = uclamp_none(UCLAMP_MAX); | |
| 1116 | + | |
| 1117 | + uclamp_se_set(&p->uclamp_req[clamp_id], clamp_value, false); | |
| 1092 | 1118 | } |
| 1093 | 1119 | } |
| 1094 | 1120 |