Messages in this thread |  | | Subject | Re: [Patch v9 7/8] sched/fair: Enable tuning of decay period | From | Dietmar Eggemann <> | Date | Tue, 4 Feb 2020 09:39:12 +0100 |
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On 03/02/2020 16:55, Peter Zijlstra wrote: > On Mon, Feb 03, 2020 at 07:07:57AM -0500, Thara Gopinath wrote: >> 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. > > Or just send an update for this patch? I'm thinking most of this is > looking good.
I do agree. IMHO, there are just two little things outstanding:
(1) arch_scale_thermal_pressure() instead of arch_cpu_thermal_pressure() in v8 4/7
(2) guarding of thermal pressure code in Arm's arch_topology driver w/ CONFIG_HAVE_SCHED_THERMAL_PRESSURE plus disabling it by default for Arm64.
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