[Nexus 5 General] Dr.Pepper:
I have created this thread to discuss what cpu and gpu governors are best for battery life, why do you use such governor or scheduler and etc!

Feel free for posting your own opinion,battery results!

But dont forget to wrtie which

KERNEL

do you use.

Usefull information:

CPU governors:

1: OnDemand

2: OndemandX

3: Performance

4: Powersave

5: Conservative

6: Userspace

7: Min Max

8: Interactive

9: InteractiveX

10: Smartass

11: SmartassV2

12: Scary

13: Lagfree

14: Smoothass

15: Brazilianwax

16: SavagedZen

17: Lazy

18: Lionheart

19: LionheartX

20: Intellidemand

21: Hotplug

22: BadAss

23: Wheatley

24: Lulzactive

25: Pegasusq/Pegasusd

26: hotplugx

27: AbissPlug

28: MSM DCVS

29: IntelliActive

30: Adaptive

31: Nightmare

32: ZZmove

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 is so because users are vastly more likely to ***** about performance than they are the few hours of extra battery life another governor could have granted them.

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. I personally feel ondemand/ondemandx goes best with SIO I/O scheduler.

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 352Mhz (or if your min frequency is higher than 352 – why?! – it will cap it to your min frequency). 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. Another favorite for many a people. 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 (= 70%, cpu is scaled up 2 steps - to 800.

If current frequency =1200, Every down_sampling_time Us if cpu load < 70%, cpu is scaled down 1 step - to 1000.

25: Pegasusq/Pegasusd

The Pegasus-q / d is a multi-core based on the Ondemand governor and governor with integrated hot-plugging.

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 'a Hotplug modified and optimized for the suspension in off-screen

27: AbissPlug

It 'a Governor derived 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.

A Krait CPU can smoothly scale from low power, low

leakage mode to blazingly fast performance.

Believe it's a governor that is mfg'd by qualcomm to utilize new on chip features.

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

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

increases so that the system is more responsive to

interactive workloads in loweset steady-state but to

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

ZZmove Governor optimized for low power consumption with the screen off, with particular attention to the limitation of consumption applications in the background with the screen off, such as listening to music. It has three settings: battery saver, balanced and performance. In addition to a performance boost, there is also the governor zzmove optimized.

I/O schedulers:

1) Noop

Inserts all the incoming I/O requests to a First In First Out queue and implements request merging. Best used with storage devices that does not depend on mechanical movement to access data (yes, like our flash drives). Advantage here is that flash drives does not require reordering of multiple I/O requests unlike in normal hard drives.

Advantages:

Serves I/O requests with least number of cpu cycles. (Battery friendly?)

Best for flash drives since there is no seeking penalty.

Good throughput on db systems.

Disadvantages:

Reduction in number of cpu cycles used is proportional to drop in performance.

2) Deadline

Goal is to minimize I/O latency or starvation of a request. The same is achieved by round robin policy to be fair among multiple I/O requests. Five queues are aggressively used to reorder incoming requests.

Advantages:

Nearly a real time scheduler.

Excels in reducing latency of any given single I/O.

Best scheduler for database access and queries.

Bandwidth requirement of a process - what percentage of CPU it needs, is easily calculated.

Like noop, a good scheduler for solid state/flash drives.

Disadvantages:

When system is overloaded, set of processes that may miss deadline is largely unpredictable.

3) CFQ

Completely Fair Queuing scheduler maintains a scalable per-process I/O queue and attempts to distribute the available I/O bandwidth equally among all I/O requests. Each per-process queue contains synchronous requests from processes. Time slice allocated for each queue depends on the priority of the 'parent' process. V2 of CFQ has some fixes which solves process' i/o starvation and some small backward seeks in the hope of improving responsiveness.

Advantages:

Considered to deliver a balanced i/o performance.

Easiest to tune.

Excels on multiprocessor systems.

Best database system performance after deadline.

Disadvantages:

Some users report media scanning takes longest to complete using CFQ. This could be because of the property that since the bandwidth is equally distributed to all i/o operations during boot-up, media scanning is not given any special priority.

Jitter (worst-case-delay) exhibited can sometimes be high, because of the number of tasks competing for the disk.

4) BFQ

Instead of time slices allocation by CFQ, BFQ assigns budgets. Disk is granted to an active process until it's budget (number of sectors) expires. BFQ assigns high budgets to non-read tasks. Budget assigned to a process varies over time as a function of it's behavior.

Advantages:

Believed to be very good for usb data transfer rate.

Believed to be the best scheduler for HD video recording and video streaming. (because of less jitter as compared to CFQ and others)

Considered an accurate i/o scheduler.

Achieves about 30% more throughput than CFQ on most workloads.

Disadvantages:

Not the best scheduler for benchmarking.

Higher budget assigned to a process can affect interactivity and increased latency.

5) SIO

Simple I/O scheduler aims to keep minimum overhead to achieve low latency to serve I/O requests. No priority quesues concepts, but only basic merging. Sio is a mix between noop & deadline. No reordering or sorting of requests.

Advantages:

Simple, so reliable.

Minimized starvation of requests.

Disadvantages:

Slow random-read speeds on flash drives, compared to other schedulers.

Sequential-read speeds on flash drives also not so good.

6) V(R)

Unlike other schedulers, synchronous and asynchronous requests are not treated separately, instead a deadline is imposed for fairness. The next request to be served is based on it's distance from last request.

Advantages:

May be best for benchmarking because at the peak of it's 'form' VR performs best.

Disadvantages:

Performance fluctuation results in below-average performance at times.

Least reliable/most unstable.

7) Anticipatory

Based on two facts

i) Disk seeks are really slow.

ii) Write operations can happen whenever, but there is always some process waiting for read operation.

So anticipatory prioritize read operations over write. It anticipates synchronous read operations.

Advantages:

Read requests from processes are never starved.

As good as noop for read-performance on flash drives.

Disadvantages:

'Guess works' might not be always reliable.

Reduced write-performance on high performance disks.

Credits go to Google and XDA forum for provided information!