From: Thara Gopinath <thara.gopinath@linaro.org>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>,
mingo@redhat.com, ionela.voinescu@arm.com,
vincent.guittot@linaro.org, rui.zhang@intel.com,
qperret@google.com, daniel.lezcano@linaro.org,
viresh.kumar@linaro.org, rostedt@goodmis.org, will@kernel.org,
catalin.marinas@arm.com, sudeep.holla@arm.com,
juri.lelli@redhat.com, corbet@lwn.net,
linux-kernel@vger.kernel.org, amit.kachhap@gmail.com,
javi.merino@kernel.org, amit.kucheria@verdurent.com
Subject: Re: [Patch v9 7/8] sched/fair: Enable tuning of decay period
Date: Fri, 7 Feb 2020 17:42:20 -0500 [thread overview]
Message-ID: <5E3DE7CC.3060300@linaro.org> (raw)
In-Reply-To: <cc83634f-b3af-6024-7f89-9b231b153070@arm.com>
On 02/04/2020 03:39 AM, Dietmar Eggemann wrote:
> 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
The "scale_" part was discussed in v6. Ionela had suggested that having
"scale" is not suited for this function because "thermal pressure" is
not exactly scaled but subtracted. I actually agree with that.
https://lore.kernel.org/lkml/20191223175005.GA31446@arm.com/
Having said that if everyone feel the same about naming of this
function, I can change it one last time.
>
> (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.
It was enabled by default as per your suggestion in v9.
The patch can be dropped.
I don't understand the need to guard arch_topology with
CONFIG_HAVE_SCHED_THERMAL_PRESSURE. CONFIG_HAVE_SCHED_THERMAL_PRESSURE
is for scheduler to enable/disable averaging of thermal pressure. We
wanted to separate updating and retrieving of instantaneous thermal
pressure from scheduler. Guarding it with
CONFIG_HAVE_SCHED_THERMAL_PRESSURE is to me equivalent to putting back
this whole code in the scheduler framework. I am against it. I also do
not see other arch_ functions guarded similarly.
>
--
Warm Regards
Thara
next prev parent reply other threads:[~2020-02-07 22:42 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-28 22:35 [Patch v9 0/8] Introduce Thermal Pressure Thara Gopinath
2020-01-28 22:36 ` [Patch v9 1/8] sched/pelt: Add support to track thermal pressure Thara Gopinath
2020-02-13 12:29 ` Amit Kucheria
2020-02-13 14:11 ` Thara Gopinath
2020-02-13 14:41 ` Amit Kucheria
2020-01-28 22:36 ` [Patch v9 2/8] sched/topology: Add hook to read per cpu " Thara Gopinath
2020-01-28 22:36 ` [Patch v9 3/8] arm,arm64,drivers:Add infrastructure to store and update instantaneous " Thara Gopinath
2020-02-13 12:25 ` Amit Kucheria
2020-02-13 14:05 ` Thara Gopinath
2020-02-13 14:38 ` Amit Kucheria
2020-02-14 15:01 ` Thara Gopinath
2020-01-28 22:36 ` [Patch v9 4/8] sched/fair: Enable periodic update of average " Thara Gopinath
2020-01-28 22:36 ` [Patch v9 5/8] sched/fair: update cpu_capacity to reflect " Thara Gopinath
2020-02-13 12:47 ` Amit Kucheria
2020-02-13 14:12 ` Thara Gopinath
2020-02-13 13:39 ` Amit Kucheria
2020-02-14 14:52 ` Thara Gopinath
2020-01-28 22:36 ` [Patch v9 6/8] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping Thara Gopinath
2020-01-28 22:36 ` [Patch v9 7/8] sched/fair: Enable tuning of decay period Thara Gopinath
2020-01-28 23:56 ` Randy Dunlap
2020-02-03 12:07 ` Thara Gopinath
2020-02-03 15:55 ` Peter Zijlstra
2020-02-04 8:39 ` Dietmar Eggemann
2020-02-07 22:42 ` Thara Gopinath [this message]
2020-02-10 11:59 ` Dietmar Eggemann
2020-02-13 13:54 ` Thara Gopinath
2020-02-14 10:26 ` Dietmar Eggemann
2020-02-18 14:57 ` Thara Gopinath
2020-02-19 9:14 ` Dietmar Eggemann
2020-01-28 22:36 ` [Patch v9 8/8] arm64: Enable averaging of thermal pressure for arm64 based SoCs Thara Gopinath
2020-02-03 8:59 ` Dietmar Eggemann
2020-02-10 12:07 ` [Patch v9 0/8] Introduce Thermal Pressure Dietmar Eggemann
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