Re: [Patch v3 7/7] sched: thermal: Enable tuning of decay period

Thara Gopinath
2019-10-21T21:04:01Z

Hi Quentin,

Thanks for the review.
On 10/15/2019 06:14 AM, Quentin Perret wrote:
> Hi Thara,
>
> On Sunday 13 Oct 2019 at 20:58:25 (-0400), Thara Gopinath wrote:
>> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
>> index 00fcea2..5056c08 100644
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -376,6 +376,13 @@ static struct ctl_table kern_table[] = {
>> .mode = 0644,
>> .proc_handler = proc_dointvec,
>> },
>> + {
>> + .procname = "sched_thermal_decay_coeff",
>> + .data = &sysctl_sched_thermal_decay_coeff,
>> + .maxlen = sizeof(unsigned int),
>> + .mode = 0644,
>> + .proc_handler = proc_dointvec,
>
> Perhaps change this for 'sched_proc_update_handler' with min and max
> values ? Otherwise userspace is allowed to write nonsensical values
> here. And since sysctl_sched_thermal_decay_coeff is used to shift, this
> can lead to an undefined behaviour.
Will do
>
> Also, could we take this sysctl out of SCHED_DEBUG ? I expect this to be
> used/tuned on production devices where SCHED_DEBUG should theoretically
> be off.

I will take it out of SCHED_DEBUG. I am wondering if this should be
a runtime control at all. Because this is a shift this changes the
accumulating window for the thermal pressure signal. A runtime change
will not guarantee a clean start of the window. May be I should make
this a config option.

>
> Thanks,
> Quentin
>

--
Warm Regards
Thara