Download - Kernel Recipes 2015: Introduction to Kernel Power Management

IntroductiontoKernelPowerManagement

KevinHilman,[email protected]

KernelRecipes2015,Paris

Idle 1

µC

CPUL2$

GPU DSPCPUL2$

Memory

DynamicPM-basedon"activity"-ActivePMSavepowerwhendoing "something "

-IdlePMSavepowerwhendoing "nothing "

Static

Complexityisgrowing...-moreCPUs-moreintegrateddevices-morepowerdomains-microcontrollers-firmware,etc.

Kernel�is�evolving....

StaticPM,SystemPM-traditionalsuspend/resumeCONFIG_PM_SLEEP=y-systemwide,alldevices-initiatedbyuserspace-anydevicecanpreventsuspend

-userspaceis"frozen"(c.f.Documentation/power/freezing-of-tasks.txt)

MUSTRead:Documentation/power/devices.txt

2

µC

IntroductiontoKernel

PowerManagement

KevinHilman,L inaro

[email protected]

Ker nel Recipes 2015, Par is

CPUL2$

GPU DSPCPUL2$

Memory

Phew...

thatwasalljustabaddream

AnyQuestions?

DynamicPM- bas ed on "act i vi t y"- Act i ve PM Save power when doi ng "s om et hi ng"

- I dl e PM Save power when doi ng "not hi ng"

structdev_pm_opsExistsinstructd evice_ d river, structb us_ typ e, . . .

structdev_pm_ops{int(*prepare)(structdevice*dev);void(*complete)(structdevice*dev);int(*suspend)(structdevice*dev);int(*resume)(structdevice*dev);...int(*suspend_late)(structdevice*dev);int(*resume_early)(structdevice*dev);...};

->begin()

->prepare()

->enter()

->wake()

->finish()

->end()

echomem>/sys/power/state

->prepare()

->suspend()

->suspend_late()

->suspend_noirq()

->resume_noirq()

->resume_early()

->resume()

->complete()

Pla tfo rmspec i fic : structplatform_suspend_ops

Per-devic e :structdev_pm_ops

pm_wakeup_event()

WakeupfromSuspendSub system/Drivercontrol:-device_init_wakeup(dev,bool)-dev_pm_set_wake_irq()-dev_pm_clear_wake_irq()

Whenwak eup occurs(e.g. inISR):-pm_wakeup_event()

Enab le/d isab lefromusersp ace:-/sys/devices/.../power/wakeup

ActivePM:UnderlyingFrameworks

Frequenc ysc a l ing :c loc k framework-clk_get_rate()-clk_set_rate()

Vo l tage sc a l ing :regu la to rframework-regulator_get_voltage()-regulator_set_voltage()-Documentation/power/regulator/consumer.txt

Examp le.. . drivers/cpufreq/cpufreq-dt.c

OperatingPerformancePointsOPPs

-tup leoffreq uency,minimumvoltage-Describ ed inDTcpu0:cpu@0{operating-points=</*kHzuV*/30000010250006000001200000800000131300010080001375000>;}

c.f.Documentation/power/opp.txt

CPUDVFS usingCPUFreq

-S elect"b est"OPPb ased onreq uirements

-p luggab legovernorsforselecting"b est"OPP-p erformance,p owersave, . . . -ond emand :h eursiticsb ased onload ,tunab le- interactive:ond emand ++,tuned forlatency

Documentation/cpu-freq/core.txt

. . . wh atab outd eviceDVFS?. . . . d evfreq

IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y

-stop p eriod ictick wh enid le-onlywak esfornext"event"orinterrup t

IdleforCPUs

CPUid lestatesh ave"d ep th "-morep owersavings- longerwak eup latency

S tateDefinitionsinDT-legacy:p latform-sp ecificd river

S tateentry-p latform-sp ecifich ook s-b ased oncompatiblestring

Idlefordevices:RuntimePM

-p er-d eviceid le-singled eviceatatime-id lenesscontrolled b yd river, b ased onactivity

-d evicesare ind epend ent-oned evicecannotp reventoth ersfromruntimesusp end ing

-d oesNOTaffectusersp ace

Don' twak eup .. .onlytop resssnoozeand gob ack tosleep

CPUid le :Howdeepto sleep?

drivers/cpuidle/governors/menu.c1)Break even po in t(basedon en te r/exi t times)- looks at pr edict able event s ( e. g. t im er s)- compar es against m in r esidency

2)La tenc yto le ranc e - checks Q oS (PM_QOS_CPU_DMA_LATENCY)- compar es against m in r esidency

3) Perfo rmanc e Impac t:- black m agic "m ult iplier " based on load- f avor shallower st at es under heavy load

Limitations:-notverySMPormulti-clusteraware

i d l e - s t a t e s {

C P U _ S T B Y : s t a n d b y {

c o m p a t i b l e = " q c o m , i d l e - s t a t e - s t b y " ,

" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 > ;

e x i t - l a t e n c y - u s = < 1 > ;

m i n - r e s i d e n c y - u s = < 2 > ;

} ;

C P U _ S P C : s p c {

c o m p a t i b l e = " q c o m , i d l e - s t a t e - s p c " ,

" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 5 0 > ;

e x i t - l a t e n c y - u s = < 2 0 0 > ;

m i n - r e s i d e n c y - u s = < 2 0 0 0 > ;

} ;

} ;

c p u @ 0 {

[ . . . ]

c p u - i d l e - s t a t e s = < & C P U _ S T B Y & C P U _ S P C > ;

} ;

D o c u m e n t a t i o n / d e v i c e t r e e / b i n d i n g s / a r m / i d l e - s t a t e s . t x t

structdev_pm_ops{

...

int(*runtime_suspend)(structdevice*dev);

int(*runtime_resume)(structdevice*dev);

int(*runtime_idle)(structdevice*dev);

};

RuntimePMAPI

Te l l PM c o re whe the rdevic e is in use"I'mabou tto u se it" -pm_runtime_get(),_sync() - I ncr em ent use count , pm _r unt im e_r esume( )

"I'mdone .. .f o rn ow"-pm_runtime_put(),_sync()-Decr em ent use count , pm _r unt im e_idle( )Sim ilar t o legacy clock f r am ewor k usage f or clock gat ing-clk_enable(),clk_disable()

Exc e l len t: Documentation/power/pm_runtime.txt

RuntimePM:callbacks

Use c oun t:1 -->0-->runtime_suspend()- pr epar e f or low- power st at e- ensur e wakeups enabled- save cont ext

Use c oun t:0 -->1-->runtime_resume()- r est or e cont ext- et c.

Aut osuspend - - - def er r ed r unt im e suspend- pm_runtime_set_autosuspend_delay()- pm_runtime_mark_last_busy()- pm_runtime_put_autosuspend()

Idlefordevices:Grouping

Devic esa re o ften groupedin to doma ins-powerga tedasa group-c an be nested-powerga ting hasla tenc yimpl ic a tions-e xte rna l regu la to rrampup,e tc .Documentation/power/devices.txt

Static DynamicSuspendResume

ActiveIdle

OPPs

CPUfreqRuntimePM

Wakeups

IdleCPUs Idledevices

CPUidle

PMdomainsNOHZ_IDLE

PMQoS

Clocks Regulators

µC

CPUL2$

GPU DSPCPUL2$

Memory

structdev_pm_domain{

structdev_pm_opsops;

...

};

GenericPMDomains(genpd)

Generic implemen ta tion o fPM domains-Basedon run time PM-When a l l devic esin doma in a re run time suspended...genpd->power_off()-When fi rstdevic e in doma in isrun time resumed...genpd->power_on()

genpdgove rno rs-a l l owc ustomdec ision mak ing be fo re powerga ting -e .g .pe r-devic e QoSc onstra in ts

genpdinDTExample genpd:power:power-controller@12340000{

compatible="foo,power-controller";

reg=<0x123400000x1000>;

#power-domain-cells=<1>;

};

Example use bydevic e :leaky-device@12350000{

compatible="foo,i-leak-current";

reg=<0x123500000x1000>;

power-domains=<&power0>;

};

Fr om : Documentation/devicetree/bindings/power/power-domain.txt

RuntimePM,genpdideas

Uni fy id le fo rCPUsanddevic es

- use r unt im e PM f or CPUs

- use r unt im e PM f or CPU- connect ed " ext r as"

( e. g. G I C, PMUs, VFP, Cor eSight , et c. )

- combine int o a " CPU genpd"

Extendto CPUCluste rs

- m odel clust er s as genpd m ade up of " CPU genpd" s

plus shar ed L2$

- when CPUs in clust er ar e idle ( r unt im e suspended)

clust er genpd can hit low- power st at e ( of f )

NextSteps

Quality:PMQoS

System-wide :e .g PM_QOS_CPU_DMA_LATENCY- Used by CPUidle t o det erm ine dept h of idle st at e

Per-devic e- at t ach Q oS const r aint s wit h specif ic devices- genpd: pr event PM domain power of f - PM_QOS_FLAG_NO_POWER_OFF

- e. g. genpd: per - device wakeup lat ency - DEV_PM_QOS_RESUME_LATENCY - f or use by genpd " gover nor s"

Documentation/power/pm_qos_interface.txt

Energy-awarescheduling:EAS

Anon -go ing e ffo rt to improve ene rgye ffic ienc yo fthe sc hedu le r.

-Teac h the sc hedu le rnewheu ristic sfo rtask p lac ementto

tak e advan tage o fene rgy-saving hardware

-In tegra te CPUid le andCPUfreqwi th the sc hedu le r

-sc hedu le rtrac k sloadsta tistic sfo r i tsown dec ision mak ing

(e .g .task p lac ement, l oadba lanc ing ,e tc .)

-CPUid le /CPUfreqgove rno rdec isionsa re basedon the i r

own load-basedc a lc u la tions,heu ristic s(andsome b lac k magic ).

These a re to be replac edbysc hedu le r-driven da ta

WorkinProgress



Drivermodel: keyconcept

S taticPM,S ystemPM-trad itionalsusp end /resumeCONFIG_PM_SLEEP=y-systemwid e,alld evices-initiated b yusersp ace-anyd evicecanp reventsusp end

-usersp aceis"frozen" ( c. f . Documentation/power/freezing-of-tasks.txt)

MUSTRead :Documentation/power/devices.txt

Linux:PM domains-ove rride opsfo ra g roupo fdevic es- i fPM domain presen t,PM c o re usesdoma in c a l lbac k sinsteado ftype /c lass/bus

Documentation/cpuidle/*.txt

3

StaticStaticPM,SystemPM-traditionalsuspend/resumeCONFIG_PM_SLEEP=y-systemwide,alldevices-initiatedbyuserspace-anydevicecanpreventsuspend

-userspaceis"frozen"(c.f.Documentation/power/freezing-of-tasks.txt)

MUSTRead:Documentation/power/devices.txt

4

structdev_pm_opsExistsinstructdevice_driver,structbus_type,...

structdev_pm_ops{

int(*prepare)(structdevice*dev);

void(*complete)(structdevice*dev);

int(*suspend)(structdevice*dev);

int(*resume)(structdevice*dev);

...

int(*suspend_late)(structdevice*dev);

int(*resume_early)(structdevice*dev);

...

};

Drivermodel:keyconcept5

->begin()

->prepare()

->enter()->wake()

->finish()

->end()


->prepare()->suspend()

->suspend_late()->suspend_noirq()

->resume_noirq()->resume_early()

->resume()->complete()

Platformspecific:structplatform_suspend_ops

Per-device:structdev_pm_ops

SuspendResume

6

WakeupfromSuspendSubsystem/Drivercontrol:-device_init_wakeup(dev,bool)-dev_pm_set_wake_irq()-dev_pm_clear_wake_irq()

Whenwakeupoccurs(e.g.inISR):-pm_wakeup_event()

Enable/disablefromuserspace:-/sys/devices/.../power/wakeup

7

µC


PowerManagement

KevinHilman,L inaro

[email protected]


CPUL2$

GPU DSPCPUL2$

Memory

Phew...


AnyQuestions?





->begin()

->prepare()

->enter()

->wake()

->finish()

->end()


->prepare()

->suspend()

->suspend_late()

->suspend_noirq()

->resume_noirq()

->resume_early()

->resume()

->complete()



pm_wakeup_event()
















IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y


IdleforCPUs

















" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 > ;

e x i t - l a t e n c y - u s = < 1 > ;

m i n - r e s i d e n c y - u s = < 2 > ;

} ;

C P U _ S P C : s p c {


" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 5 0 > ;

e x i t - l a t e n c y - u s = < 2 0 0 > ;

m i n - r e s i d e n c y - u s = < 2 0 0 0 > ;

} ;

} ;

c p u @ 0 {

[ . . . ]


} ;


structdev_pm_ops{

...




};

RuntimePMAPI




RuntimePM:callbacks







ActiveIdle

OPPs

CPUfreqRuntimePM

Wakeups


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

Clocks Regulators

µC

CPUL2$

GPU DSPCPUL2$

Memory



...

};






reg=<0x123400000x1000>;


};



reg=<0x123500000x1000>;


};










plus shar ed L2$



NextSteps

Quality:PMQoS















WorkinProgress









8

DynamicPM-basedon"activity"-ActivePMSavepowerwhendoing"something"

-IdlePMSavepowerwhendoing"nothing"

Dynamic9


Frequencyscaling:clockframework-clk_get_rate()-clk_set_rate()

Voltagescaling:regulatorframework-regulator_get_voltage()-regulator_set_voltage()-Documentation/power/regulator/consumer.txt

Example...drivers/cpufreq/cpufreq-dt.c


-tupleoffrequency,minimumvoltag e-DescribedinDTcpu0:cpu@0{operating-points=</*kHzuV*/30000010250006000001200000800000131300010080001375000>;}


CPUDVFSusing CPUFreq

-Select"best"OPPbasedonrequirements

-pluggablegovernorsforselecting"best"OPP-performance,powersave,...-ondemand:heursiticsbasedonload,tunable-interactive:ondemand++,tunedforlatency


...whataboutdeviceDVFS?....devfreq

Active

OPPs

CPUfreq

Clocks Regulators

10


-tupleoffrequency,minimumvoltage-DescribedinDTcpu0:cpu@0{operating-points=</*kHzuV*/30000010250006000001200000800000131300010080001375000>;}


OPPs11

CPUDVFSusingCPUFreq

-Select"best"OPPbasedonrequirements

-pluggablegovernorsforselecting"best"OPP-performance,powersave,...-ondemand:heursiticsbasedonload,tunable-interactive:ondemand++,tunedforlatency


...whataboutdeviceDVFS?....devfreq

12


Frequencyscaling:clockframework-clk_get_rate()-clk_set_rate()

Voltagescaling:regulatorframework-regulator_get_voltage()-regulator_set_voltage()-Documentation/power/regulator/consumer.txt

Example...drivers/cpufreq/cpufreq-dt.c

Regulators13

µC


PowerManagement

KevinHilman,L inaro

[email protected]


CPUL2$

GPU DSPCPUL2$

Memory

Phew...


AnyQuestions?





->begin()

->prepare()

->enter()

->wake()

->finish()

->end()


->prepare()

->suspend()

->suspend_late()

->suspend_noirq()

->resume_noirq()

->resume_early()

->resume()

->complete()



pm_wakeup_event()
















IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y


IdleforCPUs

















" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 > ;

e x i t - l a t e n c y - u s = < 1 > ;

m i n - r e s i d e n c y - u s = < 2 > ;

} ;

C P U _ S P C : s p c {


" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 5 0 > ;

e x i t - l a t e n c y - u s = < 2 0 0 > ;

m i n - r e s i d e n c y - u s = < 2 0 0 0 > ;

} ;

} ;

c p u @ 0 {

[ . . . ]


} ;


structdev_pm_ops{

...




};

RuntimePMAPI




RuntimePM:callbacks







ActiveIdle

OPPs

CPUfreqRuntimePM

Wakeups


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

Clocks Regulators

µC

CPUL2$

GPU DSPCPUL2$

Memory



...

};






reg=<0x123400000x1000>;


};



reg=<0x123500000x1000>;


};










plus shar ed L2$



NextSteps

Quality:PMQoS















WorkinProgress









14


PowerManagement

KevinHilman,Linaro

[email protected]


IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y

-stopperiodictickwhenidle-onlywakesfornext"event"orinterrupt

IdleforCPUs

CPUidlestateshave"depth"-morepowersavings-longerwakeuplatency

StateDefinitionsinDT-legacy:p latform-specificdriver

Stateentry-p latform-specifichooks-basedoncompatiblestring


-per-deviceid le-singledeviceatatime-id lenesscontrolled bydriver,basedonactivity

-devicesareindependent-onedevicecannotpreventothersfromruntimesuspending

-doesNOTaffectuserspace

Don'twakeup...onlytopresssnoozeandgobacktosleep

CPUidle:Howdeeptosleep?

drivers/cpuidle/governors/menu.c1)Breakevenpoint(basedonenter/exittimes)-looksatpredictableevents(e.g.timers)-comparesagainstminresidency

2)Latencytolerance-checksQoS(PM_QOS_CPU_DMA_LATENCY)-comparesagainstminresidency

3)PerformanceImpact:-blackmagic"multiplier"basedonload-favorshallowerstatesunderheavyload


idle-states{

CPU_STBY:standby{

compatible="qcom,idle-state-stby",

"arm,idle-state";

entry-latency-us=<1>;

exit-latency-us=<1>;

min-residency-us=<2>;

};

CPU_SPC:spc{

compatible="qcom,idle-state-spc",

"arm,idle-state";




};

};

cpu@0{

[...]

cpu-idle-states=<&CPU_STBY&CPU_SPC>;

};

Documentation/devicetree/bindings/arm/idle-states.txt

structdev_pm_ops{...int(*runtime_suspend)(structdevice*dev);int(*runtime_resume)(structdevice*dev);int(*runtime_idle)(structdevice*dev);};

RuntimePMAPI

TellPMcorewhetherdeviceisinuse"I'mabouttouse it"-pm_runtime_get(),_sync()-Incrementusecount,pm_runtime_resume()

"I'mdone...fornow"-pm_runtime_put(),_sync()-Decrementusecount,pm_runtime_idle()

Similartolegacyclockframeworkusageforclockgating-clk_enable(),clk_disable()

Excellent:Documentation/power/pm_runtime.txt

RuntimePM:callbacks

Usecount:1-->0-->runtime_suspend()-prepareforlow-powerstate-ensurewakeupsenabled-savecontext

Usecount:0-->1-->runtime_resume()-restorecontext-etc.

Autosuspend---deferredruntimesuspend-pm_runtime_set_autosuspend_delay()-pm_runtime_mark_last_busy()-pm_runtime_put_autosuspend()


Devicesareoftengroupedintodomains-powergatedasagroup-canbenested-powergatinghaslatencyimplications-externalregulatorrampup,etc.

Documentation/power/devices.txt

DynamicIdle

RuntimePM


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

µCCPU

L2$

GPU DSPCPUL2$

Memory

structdev_pm_domain{structdev_pm_opsops;...};


Generic implementationofPMdomains-BasedonruntimePM-Whenalldevicesindomainareruntimesuspended...genpd->power_off()-Whenfirstdeviceindomainisruntimeresumed...genpd->power_on()

genpdgovernors-allowcustomdecisionmakingbeforepowergating-e.g.per-deviceQoSconstraints

genpdinDTExamplegenpd:

power:power-controller@12340000{compatible="foo,power-controller";reg=<0x123400000x1000>;#power-domain-cells=<1>;};

Exampleusebydevice:

leaky-device@12350000{compatible="foo,i-leak-current";reg=<0x123500000x1000>;power-domains=<&power0>;};

From:Documentation/devicetree/bindings/power/power-domain.txt


UnifyidleforCPUsanddevices

-useruntimePMforCPUs

-useruntimePMforCPU-connected"extras"

(e.g.GIC,PMUs,VFP,CoreSight,etc.)

-combineintoa"CPUgenpd"

ExtendtoCPUClusters

-modelclustersasgenpdmadeupof"CPUgenpd"s

plussharedL2$

-whenCPUsinclusterareidle(runtimesuspended)

clustergenpdcanhitlow-powerstate(off)

NextSteps

Quality:PMQoS

System-wide:e.gPM_QOS_CPU_DMA_LATENCY-UsedbyCPUidletodeterminedepthofidlestate

Per-device-attachQoSconstraintswithspecificdevices-genpd:preventPMdomainpoweroff-PM_QOS_FLAG_NO_POWER_OFF

-e.g.genpd:per-devicewakeuplatency-DEV_PM_QOS_RESUME_LATENCY-forusebygenpd"governors"



Anon-goingefforttoimproveenergyeffic iencyofthescheduler.

-Teachtheschedulernewheuristicsfortaskplacementto

takeadvantageofenergy-savinghardware

-IntegrateCPUidleandCPUfreqwiththescheduler

-schedulertracksloadstatisticsforitsowndecisionmaking

(e.g.taskplacement,loadbalancing,etc.)

-CPUidle/CPUfreqgovernordecisionsarebasedontheir

ownload-basedcalculations,heuristics(andsomeblackmagic).

Thesearetobereplacedbyscheduler-drivendata

WorkinProgress

Linux:PMdomains-overrideopsforagroupofdevices-ifPMdomainpresent,PMcoreusesdomaincallbacksinsteadoftype/class/bus


15

IdleforCPUs


StateDefinitionsinDT-legacy:platform-specificdriver

Stateentry-platform-specifichooks-basedoncompatiblestring

idle-states{CPU_STBY:standby{compatible="qcom,idle-state-stby","arm,idle-state";entry-latency-us=<1>;exit-latency-us=<1>;min-residency-us=<2>;};

CPU_SPC:spc{compatible="qcom,idle-state-spc","arm,idle-state";entry-latency-us=<150>;exit-latency-us=<200>;min-residency-us=<2000>;};};

cpu@0{[...]cpu-idle-states=<&CPU_STBY&CPU_SPC>;};


IdleCPUs

CPUidle16







17

IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y



18


PowerManagement

KevinHilman,Linaro

[email protected]


IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y


IdleforCPUs














idle-states{

CPU_STBY:standby{


"arm,idle-state";




};

CPU_SPC:spc{


"arm,idle-state";




};

};

cpu@0{

[...]


};



RuntimePMAPI





RuntimePM:callbacks







DynamicIdle

RuntimePM


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

µCCPU

L2$

GPU DSPCPUL2$

Memory







Exampleusebydevice:









ExtendtoCPUClusters


plussharedL2$



NextSteps

Quality:PMQoS















WorkinProgress



19


-per-deviceidle-singledeviceatatime-idlenesscontrolledbydriver,basedonactivity


-doesNOTaffectuserspacestructdev_pm_ops{

...




};

Idledevices

20

RuntimePMAPI

TellPMcorewhetherdeviceisinuse"I'mabouttouseit"-pm_runtime_get(),_sync()-Incrementusecount,pm_runtime_resume()




21

RuntimePM:callbacks




22


PowerManagement

KevinHilman,Linaro

[email protected]


IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y


IdleforCPUs














idle-states{

CPU_STBY:standby{


"arm,idle-state";




};

CPU_SPC:spc{


"arm,idle-state";




};

};

cpu@0{

[...]


};



RuntimePMAPI





RuntimePM:callbacks







DynamicIdle

RuntimePM


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

µCCPU

L2$

GPU DSPCPUL2$

Memory







Exampleusebydevice:









ExtendtoCPUClusters


plussharedL2$



NextSteps

Quality:PMQoS















WorkinProgress



23




µCCPU

L2$

GPU DSPCPUL2$

Memory



24


GenericimplementationofPMdomains-BasedonruntimePM-Whenalldevicesindomainareruntimesuspended...genpd->power_off()-Whenfirstdeviceindomainisruntimeresumed...genpd->power_on()


25



Exampleusebydevice:



26

Quality:PMQoS





27

µC


PowerManagement

KevinHilman,L inaro

[email protected]


CPUL2$

GPU DSPCPUL2$

Memory

Phew...


AnyQuestions?





->begin()

->prepare()

->enter()

->wake()

->finish()

->end()


->prepare()

->suspend()

->suspend_late()

->suspend_noirq()

->resume_noirq()

->resume_early()

->resume()

->complete()



pm_wakeup_event()
















IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y


IdleforCPUs

















" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 > ;

e x i t - l a t e n c y - u s = < 1 > ;

m i n - r e s i d e n c y - u s = < 2 > ;

} ;

C P U _ S P C : s p c {


" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 5 0 > ;

e x i t - l a t e n c y - u s = < 2 0 0 > ;

m i n - r e s i d e n c y - u s = < 2 0 0 0 > ;

} ;

} ;

c p u @ 0 {

[ . . . ]


} ;


structdev_pm_ops{

...




};

RuntimePMAPI




RuntimePM:callbacks







ActiveIdle

OPPs

CPUfreqRuntimePM

Wakeups


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

Clocks Regulators

µC

CPUL2$

GPU DSPCPUL2$

Memory



...

};






reg=<0x123400000x1000>;


};



reg=<0x123500000x1000>;


};










plus shar ed L2$



NextSteps

Quality:PMQoS















WorkinProgress









28

IntroductiontoKernelPowerManagementKevinHilman,[email protected]


pm_wakeup_event()


UnifyidleforCPUsanddevices-useruntimePMforCPUs-useruntimePMforCPU-connected"extras"(e.g.GIC,PMUs,VFP,CoreSight,etc.)-combineintoa"CPUgenpd"

ExtendtoCPUClusters-modelclustersasgenpdmadeupof"CPUgenpd"splussharedL2$-whenCPUsinclusterareidle(runtimesuspended)clustergenpdcanhitlow-powerstate(off)

NextStepsEnergy-awarescheduling:EAS

Anon-goingefforttoimproveenergyefficiencyofthescheduler.

-Teachtheschedulernewheuristicsfortaskplacementtotakeadvantageofenergy-savinghardware

-IntegrateCPUidleandCPUfreqwiththescheduler-schedulertracksloadstatisticsforitsowndecisionmaking(e.g.taskplacement,loadbalancing,etc.)

-CPUidle/CPUfreqgovernordecisionsarebasedontheirownload-basedcalculations,heuristics(andsomeblackmagic).


WorkinProgress

29


UnifyidleforCPUsanddevices-useruntimePMforCPUs-useruntimePMforCPU-connected"extras"(e.g.GIC,PMUs,VFP,CoreSight,etc.)-combineintoa"CPUgenpd"

ExtendtoCPUClusters-modelclustersasgenpdmadeupof"CPUgenpd"splussharedL2$-whenCPUsinclusterareidle(runtimesuspended)clustergenpdcanhitlow-powerstate(off)







WorkinProgress

30







WorkinProgress

31

µC


PowerManagement

KevinHilman,L inaro

[email protected]


CPUL2$

GPU DSPCPUL2$

Memory

Phew...


AnyQuestions?





->begin()

->prepare()

->enter()

->wake()

->finish()

->end()


->prepare()

->suspend()

->suspend_late()

->suspend_noirq()

->resume_noirq()

->resume_early()

->resume()

->complete()



pm_wakeup_event()
















IdlePM:ticklessidle

CONFIG_NOHZ_IDLE=y


IdleforCPUs

















" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 > ;

e x i t - l a t e n c y - u s = < 1 > ;

m i n - r e s i d e n c y - u s = < 2 > ;

} ;

C P U _ S P C : s p c {


" a r m , i d l e - s t a t e " ;

e n t r y - l a t e n c y - u s = < 1 5 0 > ;

e x i t - l a t e n c y - u s = < 2 0 0 > ;

m i n - r e s i d e n c y - u s = < 2 0 0 0 > ;

} ;

} ;

c p u @ 0 {

[ . . . ]


} ;


structdev_pm_ops{

...




};

RuntimePMAPI




RuntimePM:callbacks







ActiveIdle

OPPs

CPUfreqRuntimePM

Wakeups


CPUidle

PMdomainsNOHZ_IDLE

PMQoS

Clocks Regulators

µC

CPUL2$

GPU DSPCPUL2$

Memory



...

};






reg=<0x123400000x1000>;


};



reg=<0x123500000x1000>;


};










plus shar ed L2$



NextSteps

Quality:PMQoS















WorkinProgress









32

Phew...


AnyQuestions?











CreatedwithInkscape&Sozi

SlidesunderCC-BY-SA3.0

http://people.linaro.org/~kevin.hilman/conf/kr2015/

33

Download - Kernel Recipes 2015: Introduction to Kernel Power Management

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