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SubjectRe: [Patch v9 7/8] sched/fair: Enable tuning of decay period
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On 01/28/2020 06:56 PM, Randy Dunlap wrote:
> Hi,
>
> On 1/28/20 2:36 PM, Thara Gopinath wrote:
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index e35b28e..be4147b 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -4376,6 +4376,11 @@
>> incurs a small amount of overhead in the scheduler
>> but is useful for debugging and performance tuning.
>>
>> + sched_thermal_decay_shift=
>> + [KNL, SMP] Set decay shift for thermal pressure signal.
>> + Format: integer between 0 and 10
>> + Default is 0.
>> +
>
> That tells an admin [or any reader] almost nothing about this kernel parameter
> or what it does. And nothing about what unit the value is in.
> Does the value 0 disable this feature?

Thanks for the review. 0 does not disable "thermal pressure" feature. 0
means the default decay period for averaging PELT signals (which is
usually 32 but configurable) will also be applied for thermal pressure
signal. A shift will shift the default decay period.

You are right. It needs more explanation here. I will fix it and send v10.

>
>> skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
>> xtime_lock contention on larger systems, and/or RCU lock
>> contention on all systems with CONFIG_MAXSMP set.
>
>
> thanks.
>


--
Warm Regards
Thara

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