From: "Doug Smythies" <dsmythies@telus.net>
To: 'Thomas Ilsche' <thomas.ilsche@tu-dresden.de>,
'Len Brown' <lenb@kernel.org>
Cc: linux-pm@vger.kernel.org, jacob.jun.pan@linux.intel.com,
linux-kernel@vger.kernel.org, 'Len Brown' <len.brown@intel.com>
Subject: RE: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep
Date: Fri, 24 Nov 2017 09:34:18 -0800 [thread overview]
Message-ID: <000901d3654a$76411b80$62c35280$@net> (raw)
In-Reply-To: FMlqe98CNhCDuFMlsezUVk
On 2017.11.16 08:11 Thomas Ilsche wrote:
> On 2017-11-09 08:38, Len Brown wrote:
>> From: Len Brown <len.brown@intel.com>
>>
>> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
>> cpuidle to shallow idle states, there is no simple mechanism
>> to give the hardware permission to enter the deeptest state permitted by PM_QOS.
>>
>> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
>>
>> "cpuidle.use_deepest=Y" can be set at boot-time, and
>> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.
>
> This is a good option to have and can conveniently prevent idle power consumption
> issues. But that wouldn't be a reasonable default, would it?
> I still think there is an inherent need for a heuristic and a corresponding
> mitigation to avoid staying in a sleep state too long.
I think so, yes. The potential energy savings, depending on work flow, are significant.
For the idle state 0 case, I have some supporting data that I will send on
the other e-mail thread.
... Doug
WARNING: multiple messages have this Message-ID (diff)
From: "Doug Smythies" <dsmythies@telus.net>
To: "'Thomas Ilsche'" <thomas.ilsche@tu-dresden.de>,
"'Len Brown'" <lenb@kernel.org>
Cc: <linux-pm@vger.kernel.org>, <jacob.jun.pan@linux.intel.com>,
<linux-kernel@vger.kernel.org>,
"'Len Brown'" <len.brown@intel.com>
Subject: RE: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep
Date: Fri, 24 Nov 2017 09:34:18 -0800 [thread overview]
Message-ID: <000901d3654a$76411b80$62c35280$@net> (raw)
In-Reply-To: FMlqe98CNhCDuFMlsezUVk
On 2017.11.16 08:11 Thomas Ilsche wrote:
> On 2017-11-09 08:38, Len Brown wrote:
>> From: Len Brown <len.brown@intel.com>
>>
>> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
>> cpuidle to shallow idle states, there is no simple mechanism
>> to give the hardware permission to enter the deeptest state permitted by PM_QOS.
>>
>> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
>>
>> "cpuidle.use_deepest=Y" can be set at boot-time, and
>> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.
>
> This is a good option to have and can conveniently prevent idle power consumption
> issues. But that wouldn't be a reasonable default, would it?
> I still think there is an inherent need for a heuristic and a corresponding
> mitigation to avoid staying in a sleep state too long.
I think so, yes. The potential energy savings, depending on work flow, are significant.
For the idle state 0 case, I have some supporting data that I will send on
the other e-mail thread.
... Doug
next prev parent reply other threads:[~2017-11-24 17:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-09 7:38 [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep Len Brown
2017-11-09 7:51 ` Vincent Guittot
2017-11-09 21:47 ` Ramesh Thomas
2017-11-16 16:11 ` [PATCH] " Thomas Ilsche
2017-11-24 17:34 ` Doug Smythies [this message]
2017-11-24 17:34 ` Doug Smythies
-- strict thread matches above, loose matches on Subject: below --
2017-11-10 17:11 Doug Smythies
2017-11-10 17:11 ` Doug Smythies
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