Messages in this thread | | | Subject | Re: [PATCH v3 1/1] sched/uclamp: add SCHED_FLAG_UTIL_CLAMP_RESET flag to reset uclamp | From | Dietmar Eggemann <> | Date | Mon, 26 Oct 2020 10:47:11 +0100 |
| |
On 25/10/2020 08:36, Yun Hsiang wrote: > If the user wants to stop controlling uclamp and let the task inherit > the value from the group, we need a method to reset. > > Add SCHED_FLAG_UTIL_CLAMP_RESET flag to allow the user to reset uclamp via > sched_setattr syscall. > > The policy is > _CLAMP_RESET => reset both min and max > _CLAMP_RESET | _CLAMP_MIN => reset min value > _CLAMP_RESET | _CLAMP_MAX => reset max value > _CLAMP_RESET | _CLAMP_MIN | _CLAMP_MAX => reset both min and max > > Signed-off-by: Yun Hsiang <hsiang023167@gmail.com>
[...]
> @@ -1451,7 +1464,8 @@ static void __setscheduler_uclamp(struct task_struct *p, > struct uclamp_se *uc_se = &p->uclamp_req[clamp_id]; > > /* Keep using defined clamps across class changes */ > - if (uc_se->user_defined) > + if (flags != SCHED_FLAG_UTIL_CLAMP_RESET && > + uc_se->user_defined) > continue;
With:
(1) _CLAMP_RESET => reset both min and max (2) _CLAMP_RESET | _CLAMP_MIN => reset min value (3) _CLAMP_RESET | _CLAMP_MAX => reset max value (4) _CLAMP_RESET | _CLAMP_MIN | _CLAMP_MAX => reset both min and max
If you reset an RT task with (1) you don't reset its uclamp.min value.
__uclamp_update_util_min_rt_default(p) doesn't know about SCHED_FLAG_UTIL_CLAMP_RESET. It only knows user_defined and will bail early.
[...]
> - if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) > + if (likely(!flags || flags == SCHED_FLAG_UTIL_CLAMP_RESET)) > return; > > - if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { > + if (flags & SCHED_FLAG_UTIL_CLAMP_MIN) { > + if (reset) { > + clamp_value = __default_uclamp_value(p, UCLAMP_MIN); > + user_defined = false; > + } else { > + clamp_value = attr->sched_util_min; > + user_defined = true; > + }
Why do you reset for (1) in the for_each_clamp_id(clamp_id) loop and for (2)-(4) in the if (flags & SCHED_FLAG_UTIL_CLAMP_MXX) condition?
You could reset (1)-(4) in the for_each_clamp_id(clamp_id) loop? In this case you wouldn't need __default_uclamp_value().
[...]
| |