[General Topics] Saber:
Collective guide of CPU governors, I/O schedulers and other kernel variables

I present to you a wonderful collection of descriptions, comparisons and graphs of common kernel variables. Before continuing on the wonderful journey of Linux kernel tuning, please note that I am not responsible for any damage to your device or malfunction. You are in complete control over your device so please do not blindly follow without proper research. While you could use this guide to tune other devices other than a smartphone, I would recommend against doing so.

Guides:

Governors - Part 1: Post 1

Governors - Part 2: Post 2

I/O Schedulers: Post 3

CPU Governor Tuning Guide: Post 4

I/O Scheduler Tuning Guide: Post 5

Hotplug Driver Tuning Guide: Post 6

TCP Algorithms: Post 7

Other Important Information: Post 8

​

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:

OnDemand

OnDemandX

Performance

Powersave

Conservative

Userspace

Min Max

Interactive

InteractiveX

Smartass

SmartassV2

Scary

Lagfree

Smoothass

Brazilianwax

SavageZen

Lazy

Lionheart

LionheartX

Intellidemand

Hotplug

Badass

Wheatley

Lulzactive

PegasusQ\PegasusD

HotplugX

Abyssplug

MSM DCVS

Intelliactive

Adaptive

Nightmare

ZZmove

Sleepy

Hyper

SmartassH3

SLP

NeoX

ZZmanX

OndemandPlus

Dynamic Interactive (DynInteractive)

Smartmax

Ktoonservative\KtoonservativeQ

Performance may cry (PMC)

Dance Dance

AbyssPlugv2

IntelliMM

InteractivePro

Slim

Ondemand EPS

Smartmax EPS

Uberdemand

Yankactive

Impulse

Bacon

Optimax

Preservative

Touchdemand

ElementalX

Bioshock

Blu_active

Umbrella_core

ConservativeX

Hyrdxq

DevilQ

Yankasusq

Darkness

Alucard

Hellsactive

Ragingmolasses

Virtuous

Sakuractive

InteractiveX v2

Alessa

GallimaufryX

AggressiveX

Tripndroid

Wrexy

Xperience

Stockdemand

Zeneractive

InteractiveB

Aggressive

IntellidemandV2

Boostactive

Wave

Barry-Allen

Arteractive

Precognition (PrecoGOV)

Mythx_plug

PegasusQPlus

Yankdemand

HyperX

Despair

Electroactive

Electrodemand

Lionfish

Interextrem

Cafactive

Lightning

ThunderX

sched-DVFS

Intel

Frankenstein

Cyan

TheSSJactive

Chill

sprdemand

Kraken

Ironactive

Nebula

Relaxed

Crazyactive

thenewbeginning

Cultivation

Schedutil

pwrutilx

blu_schedutil

Descriptions:

HMP Governors

1: OnDemand:

Description:

Ondemand is one of the original and oldest governors available on the linux kernel. When the load placed on your CPU reaches the set threshold, the governor will quickly ramp up to the maximum CPU frequency. It has excellent fluidity because of this high-frequency bias, but it can also have a relatively negative effect on battery life versus other governors. OnDemand was commonly chosen by smartphone manufacturers in the past because it is well-tested and reliable, but it is outdated now and is being replaced by Google's Interactive governor.

2: OndemandX:

Description:

Basically an ondemand with suspend/wake profiles. No further optimization was done to Ondemand to keep it close to source as possible.

3: Performance:

Description:

The performance governor locks the phone's CPU at maximum frequency.

4: Powersave:

Description:

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

5: Conservative:

Description:

This governor 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". The original and unmodified conservative is slow and inefficient. Newer and modified versions of conservative (from some kernels) are much more responsive and are better all around for almost any use.

6: Userspace:

Description:

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

Description:

Min Max is a governor that makes use of only min & maximum frequency based on workload... no intermediate frequencies are used!

8: Interactive:

Description:

Interactive scales the clockspeed over the course of a timer set by the kernel developer (or user). 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. Because of this timer, Interactive is also better prepared to utilize intermediate clockspeeds that fall between the minimum and maximum CPU frequencies. It is significantly more responsive than OnDemand, because it's faster at scaling to maximum frequency.

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.

Interactive is the default governor of choice for today's smartphone and tablet manufacturers.

9: InteractiveX:

Description:

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

Description:

Based on interactive, performance is on par with the “old” minmax and 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 352Mhz (or if your min frequency is higher than 352 it will cap it to your min frequency).

This governor will slowly ramp down frequency when the screen is off and it could also let the frequency go to low making your phone unusable (if min frequency is not checked).

11: SmartassV2:

Description:

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 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

Description:

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 whatever the kernel developer sets it too and will 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.

13: Lagfree:

Description:

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:

Description:

The same as the Smartass “governor” But MUCH more aggressive & across the board.

15: Brazilianwax:

Description:

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

16: SavagedZen:

Description:

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

17: Lazy:

Description:

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:

Description:

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

Description:

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

20: Intellidemand:

Description:

Intellidemand aka Intelligent Ondemand from Faux is yet another governor that's based on ondemand. 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.

To sum up, this is an intelligent ondemand that enters browsing mode to limit max frequency when GPU is idling, and (exits browsing mode) by behaving like ondemand when GPU is busy; to deliver performance for gaming and such. Intellidemand does not jump to highest frequency when screen is off. Faux no longer recommends intellidemand and believes that intellidemand users should switch to intelliactive for better optimizations and performance.

21: Hotplug:

Description:

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:

Description:

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 to max frequency, If the gpu is crushed under load, badass will lift the restrictions to the cpu.

23: Wheatley:

Description:

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.

Wheatley is a more performance orientated governor as it scales more aggressively than ondemand and sticks with higher frequencies.

24:Lulzactive\LulzactiveQ:

Description:

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

Description:

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). 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 will run 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

Description:

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

27: AbyssPlug

Description:

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

28: MSM DCVS

Description:

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

Description:

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.

Created by Faux

30: Adaptive

Description:

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

Description:

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: ZZmoove

Description:

The ZZmoove 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. The unique feature with ZZmoove is that it has predefined profiles and allows profile switching.

33: Sleepy

Description:

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

Description:

The Hyper (formerly known as kenobi) is an aggressive smart and smooth governor based on the Ondemand and is equipped with several features of Ondemandx suspend profiles. It also has the fast_start deep_sleep variable and detection features. In addition, the maximum frequency is in suspend mode 500Mhz or whatever the kernel developer sets it to. This is a more smoothness oriented governor which means that it is good for performance, without sacrificing much battery life.

35: SmartassH3

Description:

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

Description:

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

37: NeoX

Description:

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

38. ZZmanx

Description:

ZZmanx is exactly the same as ZZmoove, 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

Description:

Ondemandplus is an ondemand and interactive-based governor that has additional power-saving capabilities while maintaining very snappy performance. While the interactive governor provides a modern and sleek framework, the scaling logic has been been re-written completely. Reports have found that users find ondemandplus as a more battery friendly governor. In ondemandplus, the downscaling behavior from ondemand is only very slightly modified. However, the upscaling has been modified to not scale up to maximum frequency immediately.

40. Dynamic Interactive (DynInteractive)

Description:

This governor dynamically adjusts itself according to load. That means it's settings are dynamic (always changing) and not static (not changing). Dyninteractive still obtains the same great balance between battery life and performance found in the original interactive governor and improves it even further. This is not the same as the original interactive governor because of this unique behavior.

41. Smartmax

Description:

Smartmax is a mix between ondemand and smartassv2. It behaves mostly like smartass with the concept of an "ideal" frequency. By default this is configured for battery saving, so this is NOT a gaming or benchmark governor! Additionally, to make it "snappy", smartmax has "touch poke". So input events from the touchscreen will boost the cpu for a specific time to a specific frequency. Developed by XDA user Maxwen.

42. Ktoonservative\KtoonservativeQ

Description:

Ktoonservative is based on the Conservative governor, but with the addition of new tunable variables and hotplugging. It aims to be very responsive while also being good at saving battery. This governor is highly configurable and is found in ktoonsez's kernels.

43. Performance may cry (PMC)

Description:

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

Description:

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 is a performance focused governor but also blends with some battery savings.

45. AbyssPlugv2

Description:

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

Description:

A rewrite of the old Min Max governor and has 3 cpu states: Idle, UI and Max. Intelliminmax (intellimm) governor is designed to work with the newer SOCs with fixed voltage rails (ie MSM8974+ SOCs). It is designed to work within those fixed voltage ranges in order to maximize battery performance while creating a smooth UI operations. It is battery friendly and spends most of the time at lower frequencies.

47. Interactive Pro

Description:

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

Description:

A new governor from the cm branch and the slimrom project. This is a performance optimized governor and has been tuned a lot for newer devices such as the One Plus One.

49. Ondemand EPS

Description:

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. The EPS at the end stands for Extreme power savings so this governor is biased to power savings!

50. Smartmax EPS

Description:

This governor is based on Smartmax but is optimized for 'Extreme Power Saving' (hence the EPS suffix). This means it uses less battery than the original Smartmax so it is not a very good gaming governor (again!) This is only found on newer devices.