Re: [PATCH] sched/uclamp: Fix rq->uclamp_max not set on first enqueue

Dietmar Eggemann
2021-12-01T09:20:39Z

On 30.11.21 16:41, Qais Yousef wrote:
> On 11/30/21 12:29, Valentin Schneider wrote:
>> On 30/11/21 11:23, Qais Yousef wrote:
>>> Hi Valentin
>>>
>>> On 11/26/21 10:51, Valentin Schneider wrote:
>>>> On 25/11/21 16:52, Qais Yousef wrote:
>>>>> Commit d81ae8aac85c ("sched/uclamp: Fix initialization of struct
>>>>> uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to
>>>>> match the woken up task's uclamp_max when the rq is idle. This only
>>>>> impacts the first wake up after enabling the static key. And it only

LGTM.

Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

Tested with rt-app:

"tasks": {
"task_n1": {
"util_min": 0,
"util_max": 369,
"loop": 1,
"phases": {
"p000001": {
"loop": 5,
"run": 800,
"timer": {
"period": 16000,
"ref": "task_n1"
}
}
},
"policy": "SCHED_OTHER"
}
}

w/o patch:

/* missing (1) since rq->uclamp_flags = UCLAMP_FLAG_IDLE is not set initially */
[75.002086] (3) uclamp_rq_inc_id() CPU5 p=[task_n1-0 1693] uc_se->value=369 uc_rq->value=1024
/* first dequeue to _uclamp_ idle set UCLAMP_FLAG_IDLE */
[75.013851] (2) uclamp_idle_value() CPU5 p=[task_n1-0 1693] clamp_id=1 value=369
[75.017972] (1) uclamp_idle_reset() CPU5 p=[task_n1-0 1693] clamp_id=0 value=0
/* UCLAMP_FLAG_IDLE is set -> set rq->uclamp[UCLAMP_MAX].value to *369* */
[75.017984] (1) uclamp_idle_reset() CPU5 p=[task_n1-0 1693] clamp_id=1 value=369
[75.017995] (3) uclamp_rq_inc_id() CPU5 p=[task_n1-0 1693] uc_se->value=369 uc_rq->value=*369*

w/ patch:

[63.393974] (1) uclamp_idle_reset() CPU5 p=[task_n1-0 1700] clamp_id=0 value=0
/* UCLAMP_FLAG_IDLE is set -> set rq->uclamp[UCLAMP_MAX].value to *369* */
[63.401269] (1) uclamp_idle_reset() CPU5 p=[task_n1-0 1700] clamp_id=1 value=369
[63.415513] (3) uclamp_rq_inc_id() CPU5 p=[task_n1-0 1700] uc_se->value=369 uc_rq->value=*369*
/* first dequeue to _uclamp_ idle set UCLAMP_FLAG_IDLE (again) */
[63.434781] (2) uclamp_idle_value() CPU5 p=[task_n1-0 1700] clamp_id=1 value=369
[63.449681] (1) uclamp_idle_reset() CPU5 p=[task_n1-0 1700] clamp_id=0 value=0
[63.449691] (1) uclamp_idle_reset() CPU5 p=[task_n1-0 1700] clamp_id=1 value=369
[63.449699] (3) uclamp_rq_inc_id() CPU5 p=[task_n1-0 1700] uc_se->value=369 uc_rq->value=369 …