All about CPU Governors and GPU governors

Applications needed for using these features:
1. SetCPU
2. No-frills CPU Control
3. Inbuilt Performance Settings (Only in custom roms, Free)
4. Trickster Mod


What is a CPU governor?

A CPU governor in Android controls how the CPU raises and lowers its frequency in response to the demands the user is placing on their device. Governors are especially important in smartphones and tablets because they have a large impact on the apparent fluidity of the interface and the battery life of the device over a charge.

NOTE: You cannot change your CPU governor unless your phone is rooted and you have a ROM or app that lets you make a change. Also, different kernels (the intermediary software between your phone's hardware and the operating system) offer different sets of governors.

Available CPU governors:

1.       OnDemand Governor:
This governor has a hair trigger for boosting clockspeed to the maximum speed set by the user. If the CPU load placed by the user abates, the OnDemand governor will slowly step back down through the kernel's frequency steppings until it settles at the lowest possible frequency, or the user executes another task to demand a ramp.

OnDemand has excellent interface fluidity because of its high-frequency bias, but it can also have a relatively negative effect on battery life versus other governors. OnDemand is commonly chosen by smartphone manufacturers because it is well-tested, reliable, and virtually guarantees the smoothest possible performance for the phone.

This final fact is important to know before you read about the Interactive governor: OnDemand scales its clockspeed in a work queue context. In other words, once the task that triggered the clockspeed ramp is finished, OnDemand will attempt to move the clockspeed back to minimum. If the user executes another task that triggers OnDemand's ramp, the clockspeed will bounce from minimum to maximum. This can happen especially frequently if the user is multi-tasking. This, too, has negative implications for battery life.

2.        OndemandX:
Basically an ondemand with suspend/wake profiles. This governor is supposed to be a battery friendly ondemand. When screen is off, max frequency is capped at 500 mhz. Even though ondemand is the default governor in many kernel and is considered safe/stable, the support for ondemand/ondemandX depends on CPU capability to do fast frequency switching which are very low latency frequency transitions. I have read somewhere that the performance of ondemand/ondemandx were significantly varying for different i/o schedulers. This is not true for most of the other governors.

 

3.       Performance Governor:
This locks the phone's CPU at maximum frequency. While this may sound like an ugly idea, there is growing evidence to suggest that running a phone at its maximum frequency at all times will allow a faster race-to-idle. Race-to-idle is the process by which a phone completes a given task, such as syncing email, and returns the CPU to the extremely efficient low-power state. This still requires extensive testing, and a kernel that properly implements a given CPU's C-states (low power states).

 

4.       Powersave Governor:
The opposite of the Performance governor, the Powersave governor locks the CPU frequency at the lowest frequency set by the user.

 

5.       Conservative Governor:
This biases the phone to prefer the lowest possible clockspeed as often as possible. In other words, a larger and more persistent load must be placed on the CPU before the conservative governor will be prompted to raise the CPU clockspeed. Depending on how the developer has implemented this governor, and the minimum clockspeed chosen by the user, the conservative governor can introduce choppy performance. On the other hand, it can be good for battery life.

The Conservative Governor is also frequently described as a "slow OnDemand," if that helps to give you a more complete picture of its functionality.

6.       Userspace Governor:
This governor, exceptionally rare for the world of mobile devices, allows any program executed by the user to set the CPU's operating frequency. This governor is more common amongst servers or desktop PCs where an application (like a power profile app) needs privileges to set the CPU clockspeed.

7.       Min Max
well this governor makes use of only min & maximum frequency based on workload... no intermediate frequencies are used.

8.       Interactive Governor:
Much like the OnDemand governor, the Interactive governor dynamically scales CPU clockspeed in response to the workload placed on the CPU by the user. This is where the similarities end. Interactive is significantly more responsive than OnDemand, because it's faster at scaling to maximum frequency.

Unlike OnDemand, which you'll recall scales clockspeed in the context of a work queue, Interactive scales the clockspeed over the course of a timer set arbitrarily by the kernel developer. In other words, if an application demands a ramp to maximum clockspeed (by placing 100% load on the CPU), a user can execute another task before the governor starts reducing CPU frequency. This can eliminate the frequency bouncing discussed in the OnDemand section. Because of this timer, Interactive is also better prepared to utilize intermediate clockspeeds that fall between the minimum and maximum CPU frequencies. This is another pro-battery life benefit of Interactive.

However, because Interactive is permitted to spend more time at maximum frequency than OnDemand (for device performance reasons), the battery-saving benefits discussed above are effectively negated. Long story short, Interactive offers better performance than OnDemand (some say the best performance of any governor) and negligibly different battery life.

Interactive also makes the assumption that a user turning the screen on will shortly be followed by the user interacting with some application on their device. Because of this, screen on triggers a ramp to maximum clockspeed, followed by the timer behavior described above.

9.       InteractiveX Governor:
Created by kernel developer "Imoseyon," the InteractiveX governor is based heavily on the Interactive governor, enhanced with tuned timer parameters to better balance battery vs. performance. The InteractiveX governor's defining feature, however, is that it locks the CPU frequency to the user's lowest defined speed when the screen is off.

10.   Smartass
Is based on the concept of the interactive governor.
I have always agreed that in theory the way interactive works – by taking over the idle loop – is very attractive. I have never managed to tweak it so it would behave decently in real life. Smartass is a complete rewrite of the code plus more. I think its a success. Performance is on par with the “old” minmax and I think smartass is a bit more responsive. Battery life is hard to quantify precisely but it does spend much more time at the lower frequencies.
Smartass will also cap the max frequency when sleeping to. Lets take for example the 528/176 kernel, it will sleep at 352/176. No need for sleep profiles any more!"

11.   SmartassV2:
Version 2 of the original smartass governor from Erasmux. The governor aim for an "ideal frequency", and ramp up more aggressively towards this freq and less aggressive after. It uses different ideal frequencies for screen on and screen off, namely awake_ideal_freq and sleep_ideal_freq. This governor scales down CPU very fast (to hit sleep_ideal_freq soon) while screen is off and scales up rapidly to awake_ideal_freq (500 mhz for GS2 by default) when screen is on. There's no upper limit for frequency while screen is off (unlike Smartass). So the entire frequency range is available for the governor to use during screen-on and screen-off state. The motto of this governor is a balance between performance and battery.

12.   Scary
A new governor wrote based on conservative with some smartass features, it scales accordingly to conservatives laws. So it will start from the bottom, take a load sample, if it's above the upthreshold, ramp up only one speed at a time, and ramp down one at a time. It will automatically cap the off screen speeds to 245Mhz, and if your min freq is higher than 245mhz, it will reset the min to 120mhz while screen is off and restore it upon screen awakening, and still scale accordingly to conservatives laws. So it spends most of its time at lower frequencies. The goal of this is to get the best battery life with decent performance. It will give the same performance as conservative right now, it will get tweaked over time.

13.   Lagfree:
Lagfree is similar to ondemand. Main difference is it's optimization to become more battery friendly. Frequency is gracefully decreased and increased, unlike ondemand which jumps to 100% too often. Lagfree does not skip any frequency step while scaling up or down. Remember that if there's a requirement for sudden burst of power, lagfree can not satisfy that since it has to raise cpu through each higher frequency step from current. Some users report that video playback using lagfree stutters a little.

14.   Smoothass:
The same as the Smartass “governor” But MUCH more aggressive & across the board this one has a better battery life that is about a third better than stock KERNEL

15.   Brazilianwax:
Similar to smartassV2. More aggressive ramping, so more performance, less battery

16.   SavagedZen:
Another smartassV2 based governor. Achieves good balance between performance & battery as compared to brazilianwax.

17.   Lazy:
This governor from Ezekeel is basically an ondemand with an additional parameter min_time_state to specify the minimum time CPU stays on a frequency before scaling up/down. The Idea here is to eliminate any instabilities caused by fast frequency switching by ondemand. Lazy governor polls more often than ondemand, but changes frequency only after completing min_time_state on a step overriding sampling interval. Lazy also has a screenoff_maxfreq parameter which when enabled will cause the governor to always select the maximum frequency while the screen is off.

18.   Lionheart:
Lionheart is a conservative-based governor which is based on samsung's update3 source.
The tunables (such as the thresholds and sampling rate) were changed so the governor behaves more like the performance one, at the cost of battery as the scaling is very aggressive.

19.   LionheartX
LionheartX is based on Lionheart but has a few changes on the tunables and features a suspend profile based on Smartass governor.

20.   Intellidemand:
Intellidemand aka Intelligent Ondemand from Faux is yet another governor that's based on ondemand. Unlike what some users believe, this governor is not the replacement for OC Daemon (Having different governors for sleep and awake). The original intellidemand behaves differently according to GPU usage. When GPU is really busy (gaming, maps, benchmarking, etc) intellidemand behaves like ondemand. When GPU is 'idling' (or moderately busy), intellidemand limits max frequency to a step depending on frequencies available in your device/kernel for saving battery. This is called browsing mode. We can see some 'traces' of interactive governor here. Frequency scale-up decision is made based on idling time of CPU. Lower idling time (<20%) causes CPU to scale-up from current frequency. Frequency scale-down happens at steps=5% of max frequency. (This parameter is tunable only in conservative, among the popular governors)
To sum up, this is an intelligent ondemand that enters browsing mode to limit max frequency when GPU is idling, and (exits browsing mode) behaves like ondemand when GPU is busy; to deliver performance for gaming and such. Intellidemand does not jump to highest frequency when screen is off.

21.   Hotplug Governor:
The Hotplug governor performs very similarly to the OnDemand governor, with the added benefit of being more precise about how it steps down through the kernel's frequency table as the governor measures the user's CPU load. However, the Hotplug governor's defining feature is its ability to turn unused CPU cores off during periods of low CPU utilization. This is known as "hotplugging."

22.   BadAss Goveronor:
Badass removes all of this "fast peaking" to the max frequency. To trigger a frequency increase, the system must run a bit with high load, then the frequency is bumped. If that is still not enough the governor gives you full throttle. (this transition should not take longer than 1-2 seconds, depending on the load your system is experiencing)
Badass will also take the gpu load into consideration. If the gpu is moderately busy it will bypass the above check and clock the cpu with 1188Mhz. If the gpu is crushed under load, badass will lift the restrictions to the cpu.

23.   Wheatley:
Building on the classic 'ondemand' governor is implemented Wheatley governor. The governor has two additional parameters. Wheatley works as planned and does not hinder the proper C4 usage for task where the C4 can be used properly. So the results show that Wheatley works as intended and ensures that the C4 state is used whenever the task allows a proper efficient usage of the C4 state. For more demanding tasks which cause a large number of wakeups and prevent the efficient usage of the C4 state, the governor resorts to the next best power saving mechanism and scales down the frequency. So with the new highly-flexible Wheatley governor one can have the best of both worlds.

Obviously, this governor is only available on multi-core devices.

24.   Lulzactive:
It's based on Interactive & Smartass governors.
Old Version: When workload is greater than or equal to 60%, the governor scales up CPU to next higher step. When workload is less than 60%, governor scales down CPU to next lower step. When screen is off, frequency is locked to global scaling minimum frequency.
New Version: Three more user configurable parameters: inc_cpu_load, pump_up_step, pump_down_step. Unlike older version, this one gives more control for the user. We can set the threshold at which governor decides to scale up/down. We can also set number of frequency steps to be skipped while polling up and down.
When workload greater than or equal to inc_cpu_load, governor scales CPU pump_up_step steps up. When workload is less than inc_cpu_load, governor scales CPU down pump_down_step steps down.

25.   Pegasusq/Pegasusd

The Pegasus-q / d is a multi-core based on the Ondemand governor and governor with integrated hot-plugging. It is quite stable and has the same battery life as ondemand. However, it is less stable than HYPER on some devices like the S2 (before the PegasusQ governor was updated).
Ongoing processes in the queue, we know that multiple processes can run simultaneously on. These processes are active in an array, which is a field called "Run Queue" queue that is ongoing, with their priority values ​​arranged (priority will be used by the task scheduler, which then decides which process to run next).

To ensure that each process has its fair share of resources, each running for a certain period and will eventually stop and then again placed in the queue until it is your turn again. If a program is terminated, so that others can run the program with the highest priority in the current queue is executed.

26.   Hotplugx

It's a modified version of Hotplug and optimized for the suspension in off-screen

27.   AbyssPlug

It's a Governor derived from hotplug, it works the same way, but with the changes in savings for a better battery.

28.   MSM DCVS

A very efficient and wide range of Dynamic Clock and Voltage Scaling (DCVS) which addresses usage models from active standby to mid and high level processing requirements. It makes the phone's CPU smoothly scale from low power, from low leakage mode to blazingly fast performance.Only to be used by Qualcomm CPUs.

MSM is the prefix for the SOC (MSM8960) and DCVS is Dynamic Clock and Voltage Scaling. Makes sense, MSM-DCVS

29.   IntelliActive

Based off Google's Interactive governor with the following enhancements:

1. self-boost capability from input drivers (no need for PowerHAL assist)
2. two phase scheduling (idle/busy phases to prevent from jumping directly to max freq
3. Checks for offline cpus and short circuits some unnecessary checks to improve code execution paths. Therefore, it avoids CPU hotplugging.

30.   Adaptive

This driver adds a dynamic cpufreq policy governor designed for latency-sensitive workloads and also for demanding performance.
This governor attempts to reduce the latency of clock so that the system is more responsive to interactive workloads in lowest steady-state but to reduce power consumption in middle operation level, level up will be done in step by step to prohibit system from going to
max operation level.

31.   Nightmare

A PegasusQ modified, less aggressive and more stable. A good compromise between performance and battery. In addition to the SoD is a prevention because it usually does not hotplug.

32.   ZZmove

The ZZmove Governor by ZaneZam is optimized for low power consumption when the screen off, with particular attention to the limitation of consumption applications in the background with the screen off, such as listening to music. ZZmoove is not a good gaming governor as it aims to save battery. This governor is still a WIP as the developer is constantly giving updates! Here are the available profiles:

for Default (set governor defaults)
for Yank Battery -> old untouched setting (a very good battery/performance balanced setting DEV-NOTE: highly recommended!)
for Yank Battery Extreme -> old untouched setting (like yank battery but focus on battery saving)
for ZaneZam Battery -> old untouched setting (a more 'harsh' setting strictly focused on battery saving DEV-NOTE: might give some lags!)
for ZaneZam Battery Plus -> NEW! reworked 'faster' battery setting (DEV-NOTE: recommended too!  )
for ZaneZam Optimized -> old untouched setting (balanced setting with no focus in any direction DEV-NOTE: relict from back in the days, even though some people still like it!)
for ZaneZam Moderate -> NEW! setting based on 'zzopt' which has mainly (but not strictly only!) 2 cores online
for ZaneZam Performance -> old untouched setting (all you can get from zzmoove in terms of performance but still has the fast down scaling/hotplugging behaving)
for ZaneZam InZane -> NEW! based on performance with new auto fast scaling active. a new experience!
for ZaneZam Gaming -> NEW! based on performance with new scaling block enabled to avoid cpu overheating during gameplay
(since version 0.9 beta4: cpu temperature threshold of 65°C enabled if exynos4 cpu temperature reading support was compiled with the governor)

33.   Sleepy

The Sleepy (formerly known as Solo) is an attempt to strike a balance between performance and battery power to create. It is based on Ondemand. It includes some tweaks like the Down_sampling variable and other features that set by the user through the sysfs of "echo" call. Sleepy is quite similar to Ondemandx.

34.   Hyper

The Hyper (formerly known as kenobi) is an aggressive smart and smooth,based on the Ondemand and is equipped with several features of Ondemandx suspend profiles. (Added by sysfs, the settings suspend_freq and suspend Imoseyon's code) is the behavior of the HYPER. It also has the fast_start deep_sleep variable and detection features. In addition, the maximum frequency is in suspend mode 500Mhz.

35.   SmartassH3

The SmartassH3 governor is designed for battery saving and not pushing the phones performance, since doing that drains battery and that's the one thing people keep asking for more of. Based on SmartassV2.

36.   SLP

It is a mix of pegasusq and ondemand. Therefore, it has a balance between battery savings and performance.

37.   NeoX

An optimized version of the pegasusq governor but with some extra tweaks for better performance. This means more battery drainage than the original PegasusQ.

38.   ZZmanx

ZZmanx is exactly the same as ZZmove, but it has been renamed because DorimanX made it into his own version (possibly better performance) . However, it still suffers from below average gaming performance. (Refer to ZZmoove description for guide on profiles)

39.   OnDemandPlus
A governor based off of OnDemand and Interactive. It provides a balance between performance, and saving battery.

40.   DynInteractive
A dynamic interactive Governor. This Governor dynamically adapts it's own CPU frequencies within your parameters based off the system(s) load.

41.   Smartmax

This is a new governor which is a mix between ondemand and smartassv2. By default this is configured for battery saving,so this is NOT a gamer governor! This is still WIP!

42.   Ktoonservative\KtoonservativeQ

A combination of ondemand and conservative. Ktoonservative contains a hotplugging variable which determines when the second core comes online. The governor shuts the core off when it returns to the second lowest frequency thus giving us a handle on the second performance factor in our CPUs behavior.

43.   Performance may cry (PMC)
A governor based on Smartmax except it's heavily tweaked for better and maximum battery life. This is not a gaming governor!

44.   Dance Dance
Based on conservative with some smartass features, it scales accordingly to conservatives laws. So it will start from the bottom, take a load sample, if it's above the upthreshold, ramp up only one speed at a time, and ramp down one at a time. It will automatically cap the off screen speeds to 245Mhz, and if your min freq is higher than 245mhz, it will reset the min to 120mhz while screen is off and restore it upon screen awakening, and still scale accordingly to conservatives laws. So it spends most of its time at lower frequencies. The goal of this is to get the best battery life with decent performance. It will give the same performance as conservative right now, it will get tweaked over time. 

45.   AbyssPlugv2
AbyssPlugv2 is a rewrite of the original CPU governor. It also fixes the problem where the governor is set only for the first core, but now governs all cores right from whatever utility you use. There have been comments on the lack of stability with this governor. 

46.   IntelliMM
A rewrite of the old Min Max governor and has 3 cpu states: Idle, UI and Max. Pretty much a smarter Min Max governor.

47.   Interactive Pro
A newer (modified) version of interactive which is optimized for devices such as the One Plus One. It is a more efficient than the original Interactive because it continuously re-evaluates the load of each CPU therefore allowing the CPU to scale efficiently.

48.   Slim
A new governor from the cm branch and the slimrom project. A performance optimized governor. Found on newer devices only such as the One Plus One. This CPU governor will fall back to be the performance governor if very high load is detected

49.   Ondemand EPS
Once again, a modified version of Ondemand and is optimized for newer devices. It is based on the Semaphore Kernel's Ondemand which is more optimized for battery life and better performance than the traditional ondemand governor. 

50.   Smartmax EPS
A newer smartmax governor that has been slightly optimized for newer devices.

51.   Uberdemand
Uberdemand is Ondemand with 2-phase feature meaning it has a soft cap at 1728 MHz so your cpu won't always go directly to max, made by Chet Kener.

52.   Yankactive
A slightly modified interactive based governor by Yank555.lu. Possibly better performance or battery life.

Hotplugging drivers:
- mpdecision (Qualcomm's default hotplugging driver)
- intelliplug (Great for performance, more customization options)
- Alucard HotPlug (A great hotplugging driver by Alucard)
Custom kernels may have their own hotplugging drivers but they are usually based on these ones.

I recommend staying with the default hotplugging driver or keeping the setting on AUTO. If you want to experiment, be sure to expect better/worse battery life!


GPU governors

Simple: It's a new governor for the gpu frequency scaling. It will allow a more fine grained control over how the gpu scales up and down then the previous ones. This means either more performance or more battery savings

Ondemand: Much like the CPU governor, Ondemand will ramp up the frequency when a load is detected. A good balance between performance and battery savings.

MSM-Adreno: The default GPU governor used by qualcomm for their adreno GPUs. It is more performance orientated than ondemand therefore it gives better performance in games but less battery life.

Performance: As the name suggests, this keeps your GPU running at the max frequency. This is a governor if you want the best possible experience in games but you don't care about your battery life.

Powersave: Like the CPU governor, this keeps your GPU running at the lowest possible frequency. Best battery life, extreme lag in games.



Categorization:

There are four different categories CPU governors can exist as.

1) Ondemand Based:
Works on "ramp-up on high load" principle. CPU busy-time is taken into consideration for scaling decisions. Members: Ondemand, OndemandX, Intellidemand, Lazy, Lagfree, PegasusQ, HYPER, Wheatley, Hotplug, HotplugX, AbyssPlug, AbyssPlugv2, Nightmare, Sleepy.
2) Conservative Based:
Works by biasing the phone to prefer the lowest possible clockspeed as often as possible. Members: Conservative, Lionheart, LionheartX

3) Interactive Based:
Works on "make scaling decision when CPU comes out of idle-loop" principle. Members: Interactive, InteractiveX, Intelliactive, Lulzactive, Luzactiveq, Smartass, SmartassV2, SmartassH3, Brazilianwax, SavagedZen, Dyninteractive.

4) Unique Category:
These do not fall into any other category above and/or possess unique attributes. Members: Userspace, Powersave, Performance, Min Max, ZZmove, MSM DCVS

5) Hybrid Category:
These have a mix of two (or more) CPU governor behaviors. Members: Smartmax, Dancedance, Performance May Cry(PMC), Ktoonservative, KtoonservativeQ


Here are some CPU Governors I recommend...


Rating system:
Best - This CPU governor is simply the best (for the category), highly recommended.
Great - This CPU governor is very good, will suit most people.
Good - This CPU governor is good, but might not suit everyone.
Requires tuning - This CPU governor requires tuning, not for beginners.

If your kernel (not the rom) doesn't have the CPU governors that has been marked as 'best', use the ones that have been marked as 'great'.


Also, if there is more than one governor marked as 'best', choose the one that is available for you. If all are available, choose any.


For performance:


Single-core:
- Performance - Best
- Min Max - Great

Multi-core:
- Performance - Best
- Min Max - Great


For battery life:

Single-core:
- Conservative - Best
- Powersave - Good

Multi-core:
- Conservative - Best
- SLP/Sleepy - Great
- Perfomance may cry (PMC) - Best
- Powersave - Good
- Ktoonservative(Q) - Great
- Smartmax - Best



For balanced battery saving and performance:


Single-core:
- Interactive/Intelliactive - Best
- Ondemand/OndemandX - Stock, Best
- SmartassV2 - Great

Multi-core:
- MSM DCSV - Great, not common
- LulzactiveQ - Requires tuning
- Intelliactive- Great
- Interactive(X) - Great
- Ondemand/OndemandX - Stock, Best
- Pegasus(q/d) - Best
- SmartassV2 - Great
- Wheatley - Good
- Hotplug/HotplugX - Good
- HYPER - Best
- ZZMove - Requires tuning
- Dancedance - Great


For gaming:

Single-core: 
- Interactive(X) - Best
- Performance - Great
- Ondemand/OndemandX - Great
- SmartassV2 - Best

Multi-core:
- Lionheart/LionheartX - Best
- Dancedance - Good
- Intelliactive - Great
- SmartassV2 - Great
- Pegasus(Q/D) - Best
- Ondemand/OndemandX - Great
- Hyper - Best
- Performance - Great
- LulzactiveQ - Best
- Intellidemand - Good

Other CPU Governors not mentioned in the recommended section are either not used by people anymore or they are not suited for most people or have been removed from kernels.

More info/Source/Credits:
XDA Forums
XDA University