[PATCH] cpuidle: mvebu: update cpuidle thresholds for Armada XP SOCs

[Daniel Lezcano]

On 03/10/2015 07:47 PM, Gregory CLEMENT wrote:
> Le 10 mars 2015 19:35:19 GMT+01:00, Daniel Lezcano <daniel.lezcano at linaro.org> a écrit :
>> On 03/10/2015 07:05 PM, Thomas Petazzoni wrote:
>>> Hello Daniel,
>>>
>>> I know you suggested a more rigorous method of determining the exit
>>> latency and target residency times, but would it be nonetheless
>>> possible to apply this patch, which clearly improves performance a
>> lot,
>>> and actually makes the code match the values used in the vendor
>> kernel?
>>>
>>> I also think this patch should be marked for stable, it fixes values
>>> introduced in commit b858fbc1919720f7f54360098ece03b383e961fa, and
>>> should therefore be backported all the way to v3.16.
>>
>> I don't have a problem to apply this patch. But I would like to have
>> confirmation from one of the Armada maintainers the tradeoff is
>> accepted
>> (less energy saving for more performance).
>
> Hi Daniel,
>
> I already gave my acked- by for this patch, so for me this tradeoff
> is acceptable.

Ah, Indeed.

Thanks.

   -- Daniel

>>
>>> On Fri, 13 Feb 2015 15:55:03 +0100 (CET), s. rannou wrote:
>>>> Originally, the thresholds used in the cpuidle driver for Armada
>> SOCs
>>>> were temporarily chosen, leaving room for improvements.
>>>>
>>>> This commit updates the thresholds for the Armada XP SOCs with
>> values
>>>> that positively impact performances:
>>>>
>>>>                                   without patch  with patch   vendor
>> kernel
>>>>    - iperf localhost (gbit/sec)   ~3.7           ~6.4         ~5.4
>>>>    - ioping tmpfs (iops)          ~163k          ~206k        ~179k
>>>>    - ioping tmpfs (mib/s)         ~636           ~805         ~699
>>>>
>>>> The idle power consumption is negatively impacted (proportionally
>> less
>>>> than the performance gain), and we are still performing better than
>>>> the vendor kernel here:
>>>>
>>>>                                   without patch   with patch  vendor
>> kernel
>>>>    - power consumption idle (W)   ~2.4            ~3.2        ~4.4
>>>>    - power consumption busy (W)   ~8.6            ~8.3        ~8.6
>>>>
>>>> There is still room for improvement regarding the value of these
>>>> thresholds, they were chosen to mimic the vendor kernel.
>>>>
>>>> This patch only impacts Armada XP SOCs and was tested on Online Labs
>>>> C1 boards. A similar approach can be taken to improve the
>> performances
>>>> of the Armada 370 and Armada 38x SOCs.
>>>>
>>>> Thanks a lot to Thomas Petazzoni, Gregory Clement and Willy Tarreau
>>>> for the discussions and tips around this topic.
>>>>
>>>> Signed-off-by: Sebastien Rannou <mxs at sbrk.org>
>>>> ---
>>>>    drivers/cpuidle/cpuidle-mvebu-v7.c | 8 ++++----
>>>>    1 file changed, 4 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/cpuidle/cpuidle-mvebu-v7.c
>> b/drivers/cpuidle/cpuidle-mvebu-v7.c
>>>> index 38e6861..3716a1f 100644
>>>> --- a/drivers/cpuidle/cpuidle-mvebu-v7.c
>>>> +++ b/drivers/cpuidle/cpuidle-mvebu-v7.c
>>>> @@ -50,17 +50,17 @@ static struct cpuidle_driver
>> armadaxp_idle_driver = {
>>>>    	.states[0]		= ARM_CPUIDLE_WFI_STATE,
>>>>    	.states[1]		= {
>>>>    		.enter			= mvebu_v7_enter_idle,
>>>> -		.exit_latency		= 10,
>>>> +		.exit_latency		= 100,
>>>>    		.power_usage		= 50,
>>>> -		.target_residency	= 100,
>>>> +		.target_residency	= 1000,
>>>>    		.name			= "MV CPU IDLE",
>>>>    		.desc			= "CPU power down",
>>>>    	},
>>>>    	.states[2]		= {
>>>>    		.enter			= mvebu_v7_enter_idle,
>>>> -		.exit_latency		= 100,
>>>> +		.exit_latency		= 1000,
>>>>    		.power_usage		= 5,
>>>> -		.target_residency	= 1000,
>>>> +		.target_residency	= 10000,
>>>>    		.flags			= MVEBU_V7_FLAG_DEEP_IDLE,
>>>>    		.name			= "MV CPU DEEP IDLE",
>>>>    		.desc			= "CPU and L2 Fabric power down",
>>>
>>>
>>>
>>
>>
>> --
>> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
>>
>> Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
>> <http://twitter.com/#!/linaroorg> Twitter |
>> <http://www.linaro.org/linaro-blog/> Blog
>
>


-- 
  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog