Related
What's the difference between / features of:
Interactive
Conservative
Ondemand
Smartass
Smartassv2
Performance (is it run at the maximum?)
Powersave (is it run at the minimum?)
And does performance for each vary per kernel? What I mean is will, say, Interactive be better than Conservative on Incredikernel AOSP but worse on Tiny GB Sense?
pianoplayer said:
What's the difference between / features of:
Interactive
Conservative
Ondemand
Smartass
Smartassv2
Performance (is it run at the maximum?)
Powersave (is it run at the minimum?)
And does performance for each vary per kernel? What I mean is will, say, Interactive be better than Conservative on Incredikernel AOSP but worse on Tiny GB Sense?
Click to expand...
Click to collapse
ondemand
Available in most kernels, and the default governor in most kernels. When the CPU load reaches a certain point (see "up threshold" in Advanced Settings), ondemand will rapidly scale the CPU up to meet demand, then gradually scale the CPU down when it isn't needed. - SetCPU website
conservative
Available in some kernels. It is similar to the ondemand governor, but will scale the CPU up more gradually to better fit demand. Conservative provides a less responsive experience than ondemand, but can save battery. - SetCPU website
performance
Available in most kernels. It will keep the CPU running at the "max" set value at all times. This is a bit more efficient than simply setting "max" and "min" to the same value and using ondemand because the system will not waste resources scanning for the CPU load. This governor is recommended for stable benchmarking. - SetCPU website
powersave
Available in some kernels. It will keep the CPU running at the "min" set value at all times. - SetCPU website
userspace
A method for controlling the CPU speed that isn't currently used by SetCPU. For best results, do not use the userspace governor. - SetCPU website
Interactive
The 'interactive' governor has a different approach. Instead of sampling the cpu at a specified rate, the governor will scale the cpu frequency up when coming out of idle. When the cpu comes out of idle, a timer is configured to fire within 1-2 ticks. If the cpu is 100% busy from exiting idle to when the timer fires then we assume the cpu is underpowered and ramp to MAX speed.
If the cpu was not 100% busy, then the governor evaluates the cpu load over the last 'min_sample_rate' (default 50000 uS) to determine the cpu speed to ramp down to.
SMARTASS GOVERNOR
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 245Mhz (or if your min frequency is higher than 245 - why?! - it will cap it to your min frequency). Lets take for example the 998/245 kernel, it will sleep at 245. No need for sleep profiles any more!
The performance for each can varry by kernel due to the fact that some devs slightly tweak the governors to their liking. Without any tweaking they should be the same accross all kernels.
Also note that tinys kernel has an interactive X governor and also a smartass 2 governor. These are basicky just tweaked versions of the original governor.
pianoplayer said:
What's the difference between / features of:
Interactive
Conservative
Ondemand
Smartass
Smartassv2
Performance (is it run at the maximum?)
Powersave (is it run at the minimum?)
And does performance for each vary per kernel? What I mean is will, say, Interactive be better than Conservative on Incredikernel AOSP but worse on Tiny GB Sense?
Click to expand...
Click to collapse
This is a good resource for governors. It is quite technical though. It doesn't include smartass though smartass is similar to smartassv2.
CPU Governors
Let me know if you still have questions after reading it.
The answer to your second question is no. The build of the governors are about 95% the same between kernels and with the exception of the smartass governors all those listed are stock android kernels.
Interactive should be smoother than conservative or ondemand but similar in performance to the smartass governors.
SmartassV2 is found to give the best performance/battery life combo across the board.
Edit: Good writeup cmlusco. In practice yes, smartassv2 is better all around I think. Interactive from Nexus S/Galaxy Nexus kernel source should be good but I've yet to be able to backport it to work on this phone property. It turns into a performance governor really.
And a side note. If the phone is actually in deep sleep state (reported by CPU Spy) the governor will not really matter then. Only time screen off matters is when it's awake but screen is off. Governor is most critical when screen is on really, so if you go for performance, screen on performance is what matters.
Edit 2: And I read some interesting viewpoints recently on maximizing battery that are different than the minimize CPU speed.
Right now I'm at 1.35GHz with Francos stock settings, so 700 for the minimum. Should I expect to see much of a loss in battery life? And what is the difference between the different governors? I could never find much info about them.
The OC itself dosent affect battery, it's how much time your phone is in whatever state(350, 700, 1350, etc..) also setting the minimum to 700 is either really good or really bad for battery, if you turn on your screen ever 5 minutes then it will be better to have it at 700 but if you only turn on your screen once every couple hours you will get much better battery with the absolute minimum. As for governors
Code:
interactive - Instead of sampling the cpu at a specified rate, the governor will scale the cpu frequency up when coming out of idle. When the cpu comes out of idle, a timer is configured to fire within 1-2 ticks. If the cpu is 100% busy from exiting idle to when the timer fires then we assume the cpu is underpowered and ramp to MAX speed.
smartass - Is an improved version of interactive governor
ondemand – Available in most kernels, and the default governor in most kernels. When the CPU load reaches a certain point (see “up threshold” in Advanced Settings), ondemand will rapidly scale the CPU up to meet demand, then gradually scale the CPU down when it isn't needed.
conservative – Available in some kernels. It is similar to the ondemand governor, but will scale the CPU up more gradually to better fit demand. Conservative provides a less responsive experience than ondemand, but can save battery.
performance – Available in most kernels. It will keep the CPU running at the “max” set value at all times. This is a bit more efficient than simply setting “max” and “min” to the same value and using ondemand because the system will not waste resources scanning for CPU load.
powersave – Available in some kernels. It will keep the CPU running at the “min” set value at all times.
userspace – A method for controlling the CPU speed that isn't currently used by SetCPU. For best results, do not use the userspace governor.
brazilianwax - Very agresive version of smartass
interactiveX - Tweaked Interactive governor by Imoseyon by adding more features like suspend/wake profile
ondemandX - Tweaked and ported from 2.6.38 base Ondemand governor by Imoseyon by adding more features like suspend/wake profile
This is taken from the lord module kernel from the desire HD forum as it has a list of many governors, you may have to try a couple governors until you find one that balances speed and battery life for your personal needs, on more governor on our devices is hotplug which will turn off one of the CPU cores when the screen is off.
Before anyone starts leaving any posts i know most of this information may not come to hand for our One X but i wanted to give people a better explanation in what a kernel is and the many more definitions of the terms mean. Also i do not take any credit for this work it is merely done by me by asking permission from the original author of the thread from the S2 forums and i thought it would be handy to have this here as it provides a lot of useful information and thought we have this thread here. Many thanks to Droidphile for allowing me to use his thread for our One X forum side. His thread is here
Most of us are flash maniacs, and we do it a lot. But after a kernel flash, we wonder:
Q1. "OK i have flashed this xyz kernel. What're all these governors? How do i know which one is the best for me? How do i tweak them to bias their characters towards Battery-life/Performance/Balance between the Two".
Q2. "What's the fuzz about these modules that comes with the kernel. How do i use them. Are they any good. Is it OK to neglect them?"
Q3. "What roles does an i/o scheduler play? How to choose a reliable i/o scheduler?"
Q4. "Can i have more control on CPU? More info and tweaks on dual core CPU, bus frequency, etc?"
Q5. "Better understanding on impact of different values for basic/advanced parameters in the Kernel Config App, so that i can tweak the settings according to my taste?"
Hope this thread could give you answers for all these questions. We're covering governors, modules, i/o schedulers that comes with Siyah kernel, plus more. That should cover almost all the popular governors/modules/io schedulers! Many people seem to get lost in Kernel dev threads without getting answers about governors and such.
The info in this thread holds good for non-siyah kernel users too. You should find here, info on most of the governors/modules/io schedulers in your kernel if not all.
POST 1: KERNEL GOVERNORS
POST 2: I/O SCHEDULERS
POST 3: LOADABLE KERNEL MODULES
1. GOVERNORS
I) MANUAL:
These are the 18 governors we're talking about.
1) Ondemand
2) Ondemandx
3) Conservative
4) Interactive
5) Interactivex
6) Lulzactive
7) Smartass
8) SmartassV2
9) Intellidemand
10) Lazy
11) Lagfree
12) Lionheart
13) LionheartX
14) Brazilianwax
15) SavagedZen
16) Userspacce
17) Powersave
18) Performance
NOTE: Info on Samsung's own multi-core aware governor - Pegasusq is here
1) Ondemand:
Default governor in almost all stock kernels. One main goal of the ondemand governor is to switch to max frequency as soon as there is a CPU activity detected to ensure the responsiveness of the system. (You can change this behavior using smooth scaling parameters, refer Siyah tweaks at the end of 3rd post.) Effectively, it uses the CPU busy time as the answer to "how critical is performance right now" question. So Ondemand jumps to maximum frequency when CPU is busy and decreases the frequency gradually when CPU is less loaded/apporaching idle. Even though many of us consider this a reliable governor, it falls short on battery saving and performance on default settings. One potential reason for ondemand governor being not very power efficient is that the governor decide the next target frequency by instant requirement during sampling interval. The instant requirement can response quickly to workload change, but it does not usually reflect workload real CPU usage requirement in a small longer time and it possibly causes frequently change between highest and lowest frequency.
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) Conservative:
A slower Ondemand which scales up slowly to save battery. The conservative governor is based on the ondemand governor. It functions like the Ondemand governor by dynamically adjusting frequencies based on processor utilization. However, the conservative governor increases and decreases CPU speed more gradually. Simply put, this governor increases the frequency step by step on CPU load and jumps to lowest frequency on CPU idle. Conservative governor aims to dynamically adjust the CPU frequency to current utilization, without jumping to max frequency. The sampling_down_factor value acts as a negative multiplier of sampling_rate to reduce the frequency that the scheduler samples the CPU utilization. For example, if sampling_rate equal to 20,000 and sampling_down_factor is 2, the governor samples the CPU utilization every 40,000 microseconds.
4) Interactive:
Can be considered a faster ondemand. So more snappier, less battery. Interactive is designed for latency-sensitive, interactive workloads. Instead of sampling at every interval like ondemand, it determines how to scale up when CPU comes out of idle. The governor has the following advantages: 1) More consistent ramping, because existing governors do their CPU load sampling in a workqueue context, but interactive governor does this in a timer context, which gives more consistent CPU load sampling. 2) Higher priority for CPU frequency increase, thus giving the remaining tasks the CPU performance benefit, unlike existing governors which schedule ramp-up work to occur after your performance starved tasks have completed. Interactive It's an intelligent Ondemand because of stability optimizations. Why??
Sampling the CPU load every X ms (like Ondemand) can lead to under-powering the CPU for X ms, leading to dropped frames, stuttering UI, etc. Instead of sampling the CPU at a specified rate, the interactive governor will check whether to scale the CPU frequency up soon after coming out of idle. When the CPU comes out of idle, a timer is configured to fire within 1-2 ticks. If the CPU is very busy between exiting idle and when the timer fires, then we assume the CPU is underpowered and ramp to max frequency.
5) Interactivex:
This is an Interactive governor with a wake profile. More battery friendly than interactive.
6) Lulzactive:
This new find from Tegrak is based on Interactive & Smartass governors and is one of the favorites.
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.
Example:
Consider
inc_cpu_load=70
pump_up_step=2
pump_down_step=1
If current frequency=200, Every up_sampling_time Us if cpu load >= 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.
7) Smartass:
Result of Erasmux rewriting the complete code of interactive governor. Main goal is to optimize battery life without comprising performance. Still, not as battery friendly as smartassV2 since screen-on minimum frequency is greater than frequencies used during screen-off. Smartass would jump up to highest frequency too often as well.
8) 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.
9) 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.
10) 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.
11) 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.
12) Lionheart:
Lionheart is a conservative-based governor which is based on samsung's update3 source. Tweaks comes from 1) Knzo 2) Morfic. The original idea comes from Netarchy. See here. 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.
To 'experience' Lionheart using conservative, try these tweaks:
sampling_rate:10000 or 20000 or 50000, whichever you feel is safer. (transition latency of the CPU is something below 10ms/10,000uS hence using 10,000 might not be safe).
up_threshold:60
down_threshold:30
freq_step:5
Lionheart goes well with deadline i/o scheduler. When it comes to smoothness (not considering battery drain), a tuned conservative delivers more as compared to a tuned ondemand.
13) LionheartX
LionheartX is based on Lionheart but has a few changes on the tunables and features a suspend profile based on Smartass governor.
14) Brazilianwax:
Similar to smartassV2. More aggressive ramping, so more performance, less battery.
15) SavagedZen:
Another smartassV2 based governor. Achieves good balance between performance & battery as compared to brazilianwax.
16) Userspace:
Instead of automatically determining frequencies, lets user set frequencies.
17) Powersave:
Locks max frequency to min frequency. Can not be used as a screen-on or even screen-off (if scaling min frequency is too low).
18) Performance:
Sets min frequency as max frequency. Use this while benchmarking!
So, Governors can be categorized into 3/4 on a high level:
1.a) 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.
1.b) Conservative Based:
Members: Conservative, Lionheart, LionheartX
2) Interactive Based:
Works on "make scaling decision when CPU comes out of idle-loop" principle. Members: Interactive, InteractiveX, Lulzactive, Smartass, SmartassV2, Brazilianwax, SavagedZen.
3) Weird Category:
Members: Userspace, Powersave, Performance.
__________________________________________________ __________________________________________________ ____________
II) QUESTION TIME:
Q. "Ok. Enough of explanations. Tell me which governor is for performance and which one is for battery life."
A. Tough question! lulzactive and smartassV2 for a balance between performance and battery. For light weight tasks, lulzactive should be better for battery. And for heavy weight tasks, lulzactive should be better for performance also. To get maximum performance, use a tweaked ondemand or conservative, but never complain about battery. NOTE: It's not so easy to tame luzactive. If you don't know how exactly to do it, stay away from it or you will end up complaining about battery drain!
Q. "Hey, almost forgot. How do i change governors?"
A. Best way is to use an init.d script if your kernel supports it. (echo "governor-name" > /sys/devices/system/cpu/cpu0/cpufreq /scaling_governor) Else use Voltage Control/SetCpu/No Frills/Antuntu CPU Master, etc. Voltage Control has the interfaces for gpu oc/uc/uv and charge-current change if your kernel supports them. Like we guessed, these apps will tell us the active governor too.
Q. "How do i know which governor is best for me?"
A. It depends on what you need and your daily usage pattern. Performance or battery. Better choose a governor that's balanced for battery/performance. Or tweak a governor to give performance an upper-hand as compared to battery. We can always re-charge the phone: In car when off to work, or overnight. But we can not recharge performance! After all, we bought GS2 to enjoy it's sheer power.
Q. "Well i have set my favorite governor as screen-on governor and another one as screen-off governor. Why the hell is the phone not waking up after deep sleep. I need to force-restart the phone by pressing power button for about 10 secs. Is it a sleep-of-death?"
A. Yes it is. Do not use two governors as screen-on & screen-off govs, if they both have an upper frequency limit for screen-off state.
Didn't get it? Examples for Wrong combinations: (screen-on:screen-off):-
ondemandX:smartassV2
Examples for right combinations:-
ondemand:smartassV2, lulzactive:smartassV2
Q. "I can feel slight lags here and there with a governor. For ex: while scrolling through app drawer/vertically scrolling browser, etc. I really love this governor and don't tell me to use another governor. Can i diminish this lag?"
A. Hmm well, you can. Basically what we have to do is make the governor "poll" less often to scale-down cpu. Increase down-sampling-time of your governor (whichever parameter that corresponds to), so that the cpu will stay longer on a frequency before scaling down. This should eliminate the lag.
Q. "Even though i don't have too much uv/oc, once in a while; may be once in two weeks, i experience a freeze/lock/reboot. I'm using governor X. How do i solve this?"
A. Well, a random reboot/freeze once in a while signifies that we're android/galaxy SII enthusiast. If everything go smooth as silk, what's the fun? We could use stock rom/kernel/governor and be happy. A rare reboot or freeze is nothing to worry about. Just restart the phone.
Q. "OK. I want to tweak these governors according to my usage pattern, because i'm not happy with the default behavior of these governors".
A. You can tweak the governors using an init.d script to echo suitable values into:
/sys/devices/system/cpu/cpufreq/name-of-active-governor/name-of-the-paramater-to-tweak
Example:
echo "20000" /sys/devices/system/cpu/cpufreq/lulzactive/up_sample_time
Q. "I'm going to set scaling min freq as 100 mhz because my kernel supports it. Hope there's nothing wrong in doing that."
A. Wait! You may want to stay away from using 100mhz during screen-off or screen-on states for three reasons 1) It seems 100 mhz uses more power than 200 mhz. According to tests, 100 mhz accounted to 1 W / GHz and 200 mhz to 0.7 W / GHz, when both the cores were online. 2) 200 mhz can finish same task faster compared 100 mhz and thus hit deep idle soon. 3) 200 mhz is the 'sweet spot' of frequency in SGS II. ie, the frequency used in the calculations based on the optimal energy to run (Ex: In Milestone it's 550 MHz). So , 'energetically efficient' frequency for our CPU is 200 mhz.
Q. "I want to know is there's anything more i can do to improve battery life. I have already tweaked my governor settings but..."
A. Take my word. Best way is to limit scaling max freq to 800 or 1000 mhz. Sgs2 can do majority of the task with 1000 or 800 as the max. OCing to 1600mhz draws considerably more power than stock 1200mhz or even 1400mhz. Try scaling between 200 and 1000 mhz for a day and feel the difference.
Q. "How to make my device more snappier. I don't care much about batt....err...I do care about battery life, but only in terms of avoiding unwanted power consumption. Device should instantly dance to my tunes."
A. Scale 500 to 1200 during screen-on and 200-500 during screen-off. Use performance tweaked conservative/ondemand(x). No excess power consumption because 1400 and 1600 is out the league. Response will be sweet. And don't worry, minimum of 500 during screen-on will not drain too much battery like you think!
I/O Schedulers in Post 2.
Many thanks again to Droidphile for his permission for the information from his thread and make this one here for the One X. Again will say most things might not be available yet for our One X but it gives a clearer indication to users about the tweaking of a kernel and definitions that kernel developers use and more advanced users. I do not take any credit for this i just merely wanted to put this thread for us here so users can read information upon any questions they might have about kernels
2. I/O SCHEDULERS
Q. "What purposes does an i/o scheduler serve?"
A.
Minimize hard disk seek latency.
Prioritize I/O requests from processes.
Allocate disk bandwidth for running processes.
Guarantee that certain requests will be served before a deadline.
So in the simplest of simplest form: Kernel controls the disk access using I/O Scheduler.
Q. "What goals every I/O scheduler tries to balance?"
A.
Fairness (let every process have its share of the access to disk)
Performance (try to serve requests close to current disk head position first, because seeking there is fastest)
Real-time (guarantee that a request is serviced in a given time)
Q. "Description, advantages, disadvantages of each I/O Scheduler?"
A.
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.
Q. "Best I/O Scheduler?"
A.There is nothing called "best" i/o scheduler. Depending on your usage environment and tasks/apps been run, use different schedulers. That's the best i can suggest.
However, considering the overall performance, battery, reliability and low latency, it is believed that
SIO > Noop > Deadline > VR > BFQ > CFQ, given all schedulers are tweaked and the storage used is a flash device.
Q. "How do i change I/O schedulers?"
Voltage Control or No Frills from market.
Or init.d script:
echo "scheduler-name" > /sys/block/mmcblk0/queue/scheduler
3. MODULES
A loadable kernel module is an object that contains some code to extend your kernel. Modules serves various type of purposes like support for new hardwares, filesystems, and system calls. It is probable that once a new module is inserted, it might cause minor fragmentation in kernel resulting in a minor performance penalty. Mostly, not noticeable.
We might ask "ok, if kernel modules are so amazing, why not add them all into the kernel code instead of asking us to load them". Well, the advantage to LKMs is that you can minimize the memory footprint for a kernel, loading only those elements that are needed.
You can find all the modules in /lib/modules. (With extension .ko = Kernel Object).
Nice info mate ...
ShyamSasi said:
Nice info mate ...
Click to expand...
Click to collapse
thanks but like i stated above i just merely asked for permission to get this thread from the originator and cherry pick the info that i thought might be useful for users here to get a better inside of kernels and the definitions..and the author of the original thread was kind enough to let me cherry pick info to use...
Hope mods allow this thread and do not move it so at least users can come here and learn more about kernels..
Goku80 said:
...and cherry pick the info that i thought might be useful for users here...
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You can only cherry pick commits from git, not knowledge! Knowledge is to be shared Be prepared to answer lotsa questions...
And btw, there are references to Siyah kernel (a custom kernel specific to GS2/GS3) that you may wanna remove. One X has nothing to do with it and users may be confused.
(Did i actually make a post in the forum of 'opponent device' of the device I own ! )
droidphile said:
You can only cherry pick commits from git, not knowledge! Knowledge is to be shared Be prepared to answer lotsa questions...
And btw, there are references to Siyah kernel (a custom kernel specific to GS2/GS3) that you may wanna remove. One X has nothing to do with it and users may be confused.
(Did i actually make a post in the forum of 'opponent device' of the device I own ! )
Click to expand...
Click to collapse
:silly: me...thought i just add the definitions you wrote regarding governors and schedulers..all the rest like tweaks and stuff not needed here...
see how this goes and take it from there..
i have to thank you again for letting me use your info for this forum mate
Great stuff, thanks!
Nice info, me learning haha..
This is good but none of the modules and their description are for the one x, any possible way to get the info for that ?.
DANOFDANGER said:
This is good but none of the modules and their description are for the one x, any possible way to get the info for that ?.
Click to expand...
Click to collapse
oh my bad apologies for that...Will work on that..will get the modules from faux kernel and will find the definitions over next week and will add them in post 3 i promise..for now i left what is the definition of modules and will add the description of each one for our phone over next week when i have more time to myself and not working...
started work again so not as much time as i use to have
Goku80 said:
oh my bad apologies for that...Will work on that..will get the modules from faux kernel and will find the definitions over next week and will add them in post 3 i promise..for now i left what is the definition of modules and will add the description of each one for our phone over next week when i have more time to myself and not working...
started work again so not as much time as i use to have
Click to expand...
Click to collapse
No worries mate much appreciated.
I DID NOT CREATE THE ORIGINAL LIST OF 20 GOVERNORS BUT I DID ADD MORE AND I DID TAKE THE TIME TO DOUBLE CHECK EACH INDIVIDUAL GOVERNOR TO MAKE SURE THEY WERE CORRECT...I MADE THIS SOLELY SO PEOPLE DONT HAVE TO GO BACK TEN PAGES TO SEE IT...a big thanks to rEcEivEr for the original thread/post I found and all the other original OP's.
If you feel any are missing or if there are new ones I missed please let me know and we'll add them....hope this helps because I see plenty of people asking.
So let's get to it...
GOVERNORS EXPLAINED
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: Dyninteractive
30: Sakuractive (Thanks to Sandman-007)
31: Ktoonservative (Thanks to EniGmA1987)
32: Zen (Thanks to EniGmA1987)
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 (<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 Governor:
Badass removes all of this "fast peaking" to the max frequency. On a typical system the cpu won't go above 918Mhz and therefore stay cool and will use less power. To trigger a frequency increase, the system must run a bit @ 918Mhz with high load, then the frequency is bumped to 1188Mhz. 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:
target_residency - The minimum average residency in µs which is considered acceptable for a proper efficient usage of the C4 state. Default is 10000 = 10ms.
allowed_misses - The number sampling intervals in a row the average residency is allowed to be lower than target_residency before the governor reduces the frequency. This ensures that the governor is not too aggressive in scaling down the frequency and reduces it just because some background process was temporarily causing a larger number of wakeups. The default is 5.
Wheatley works as planned and does not hinder the proper C4 usage for task where the C4 can be used properly .
For internet browsing the time spend in C4 has increased by 10% points and the average residency has increased by about 1ms. I guess these differences are mostly due to the different browsing behaviour (I spend the last time more multi-tabbing). But at least we can say that Wheatley does not interfere with the proper use of the C4 state during 'light' tasks. For music playback with screen off the time spend in C4 is practically unchanged, however the average residency is reduced from around 30ms to around 18ms, but this is still more than acceptable.
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:
Lulzactive:
This new find from Tegrak is based on Interactive & Smartass governors and is one of the favorites.
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.
Example:
Consider
inc_cpu_load=70
pump_up_step=2
pump_down_step=1
If current frequency=200, Every up_sampling_time Us if cpu load >= 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: Dyninterative
Similar to interactive in almost every way possible except it "dyn"amically adapts its own tunables and settings depending on system load
30: Sakuractive: This driver mimics the frequency scaling behavior in "on demand" but with several key differences. First is that frequency transitions use the CPUFreq table directly, instead of incrementing in a percentage of the maximum available frequency. Second "sakuractive" will offline auxillary CPUs when the system is idle, and online those CPUs once the system becomes busy again. This last feature is needed for architectures which transition to low power states when only the "master" CPU is online, or for thermally constrained devices
31: Ktoonservative
There is so much going on with this governor I'd rather have the makers explain it themselves....so here you go
http://forum.xda-developers.com/showthread.php?t=2032956
32: Zen
It's an FCFS (First come, first serve) based algorithm. It does not do any sorting. It uses deadlines for fairness, and treats synchronous requests with priority over asynchronous ones.
only few of them available on my gnex
ps000000 said:
only few of them available on my gnex
Click to expand...
Click to collapse
The available governors will depend on the kernel you are using.
cupfulloflol said:
The available governors will depend on the kernel you are using.
Click to expand...
Click to collapse
ps000000 said:
only few of them available on my gnex
Click to expand...
Click to collapse
Exactly what cupfulloflol said its going to depend on which kernel you are using
Re: Galaxy Nexus Governors Explained
You are missing a very popular governor: sakuractive
Toro | Atom v9 | AK Cylon 801
Sandman-007 said:
You are missing a very popular governor: sakuractive
Toro | Atom v9 | AK Cylon 801
Click to expand...
Click to collapse
Thanks I'll add it
Sandman-007 said:
You are missing a very popular governor: sakuractive
Toro | Atom v9 | AK Cylon 801
Click to expand...
Click to collapse
Updated.... thanks again Sandman
JamesPumaEnjoi said:
Updated.... thanks again Sandman
Click to expand...
Click to collapse
No prob bro. Thanks for the guide
Toro | Atom v9 | AK Cylon 801
Any chance you could do a list about io schedulers and tcp congestion profiles too?
eqjunkie829 said:
Any chance you could do a list about io schedulers and tcp congestion profiles too?
Click to expand...
Click to collapse
Absolutely... I'm actually off all next week from school I'll get started this weekend
Sandman-007 said:
No prob bro. Thanks for the guide
Toro | Atom v9 | AK Cylon 801
Click to expand...
Click to collapse
My pleasure man
Nice :thumbup:
Sent from my Galaxy using xda premium
ranalab said:
Nice :thumbup:
Sent from my Galaxy using xda premium
Click to expand...
Click to collapse
Thanks man I appreciate it
Thanks! This is a great guide and I have been looking for something like this especcialy with flashing new kernels all the time this will be a big help and a good reference.
the cronic dude said:
Thanks! This is a great guide and I have been looking for something like this especcialy with flashing new kernels all the time this will be a big help and a good reference.
Click to expand...
Click to collapse
Not a problem at all just happy its helping some people out
Great Thread :thumbup:
Inviato dal mio Galaxy Nexus con Tapatalk 2
good
good to know
SamueleCiprietti said:
Great Thread :thumbup:
Inviato dal mio Galaxy Nexus con Tapatalk 2
Click to expand...
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dizzy1k said:
good to know
Click to expand...
Click to collapse
Thanks guys glad it helped you
JamesPumaEnjoi said:
Absolutely... I'm actually off all next week from school I'll get started this weekend
Click to expand...
Click to collapse
Thank you so much for doing that , i cant find anything on TCP congestion that i can actually understand , this is the easiest guide to read about the different governors that I've come across . Great job man :thumbup:
Sent from my Galaxy Nexus using Xparent Cyan Tapatalk 2
bsmitty83 said:
Thank you so much for doing that , i cant find anything on TCP congestion that i can actually understand , this is the easiest guide to read about the different governors that I've come across . Great job man :thumbup:
Sent from my Galaxy Nexus using Xparent Cyan Tapatalk 2
Click to expand...
Click to collapse
Working on it....slowly but surely working on it . It'll be done soon
I know this kinda thread can be found easily on net, but i will keep it updated with new governors and i/o schedulers..
This is just for people who are curious what is the difference between all of them.
CPU Governors Explained:
THE USUAL GOVERNORS
1- OnDemand
2- Interactive
3- Performance
4- Powersave
5- Conservative
6- Userspace
OTHER GOVERNORS
1- OnDemandX
2- InteractiveX
3- Badass
4- Lagfree
5- Scary
6- Lazy
7- Lionheart
8- SmartassV2
9- Wheatley
10- Intellidemand
11- Lulzactive
12- Sakuractive
THE USUAL 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 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: 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.
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.
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.
OTHER GOVERNORS
1: 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.
2: InteractiveX:
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.
3: Badass
Badass removes all of this "fast peaking" to the max frequency. On a typical system the cpu won't go above 1080Mhz and therefore use less power. To trigger a frequency increase, the system must run a bit @ 1080MHz with high load, then the frequency is bumped to 1350MHz. If that is still not enough the governor gives you full throttle. (this transition should not take longer than 2-5 seconds, depending on the load your system is experiencing).
You can tweak the Phase 2 (1080MHz) and Phase 3 (1350MHz) via sysfs (if you don't know, then just leave it alone)
4: 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.
5: 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.
6: 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.
7: 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.
8: 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.
9: Wheatley:
in short words this govenor is build on “ondemand” but increases the C4 (the sleep state) state time of the CPU and doing so trying to save juice. 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.
10: 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.
11: Lulzactive:
This new find from Tegrak is based on Interactive & Smartass governors and is one of the favorites.
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.
12: Sakuractive:
This driver mimics the frequency scaling behavior in "on demand" but with several key differences. First is that frequency transitions use the CPUFreq table directly, instead of incrementing in a percentage of the maximum available frequency. Second "sakuractive" will offline auxillary CPUs when the system is idle, and online those CPUs once the system becomes busy again. This last feature is needed for architectures which transition to low power states when only the "master" CPU is online, or for thermally constrained devices.(thanks mirajkar.aniket232)
I/O Schedulers Explained
I/O:- short form of Input & Output
I/O Scheduler:- Input/output (I/O) scheduling is a term used to describe the method computer operating systems decide the order that block I/O operations will be submitted to storage volumes. I/O Scheduling is sometimes called 'disk scheduling'.
I/O schedulers can have many purposes depending on the goal of the I/O scheduler, some common goals are:
- To minimize time wasted by hard disk seeks.
- To prioritize a certain processes' I/O requests.
- To give a share of the disk bandwidth to each running process.
- To guarantee that certain requests will be issued before a particular deadline.
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.
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: FIOPS (fair in out performance scheduler) :
A new I/O scheduler was presented for the Linux kernel. This new scheduler, FIOPS, is designed around modern flash-based storage devices like solid-state drives. This new I/O scheduler is designed around the following assumptions about Flash-based storage devices: no I/O seek time, read and write I/O cost is usually different from rotating media, time to make a request depends upon the request size, and high through-put and higher IOPS with low-latency, ehich leads to a better battery consumption. The design of the Fair IOPS scheduler is similar to CFQ but the dispatch decision is made according to IOPS instead of slice, while being backed by a simple algorithm
Guide on Overclocking/Undervolting !!
Most of the people here in xda do know about overclocking and stuffs but still there are many who are so eager to overclock their beast . Hence this guide.
I have given some good info below about these stuffs as far as i can , you can always use google to get further details.
What is overclocking?
Overclocking is the process of making a computer or component operate faster than the specified clock frequency by the manufacturer by modifying system parameters. One of the most important techniques is running at a higher clock rate (more clock cycles per second; hence the name "overclocking")
Operating voltages may also be changed (increased), which can increase the speed at which operation remains stable.
Advantage:
You can get more performance from your chipset, you can see the visible changes in application execution time and much more like instant response time.
Disadvantage:
* Overclocking is always risky if something is configured improperly and may also result in permanent damage of your hardware. As long as it is done safely you are good to go.
* You may see some increased power consumption.
* Extreme overclocking might kill your hardware.
Undervolting :
The process where you provide less voltage to your cpu rather than the stock voltage.
Advantage:
* Reduced heat from your device.
* Good battery life.
Disadvantage:
* Extreme undervolting will make your device unstable and some times even end up with a boot loop.
Requirements:
1. Kernel with overclocking support.
2. Tools to change frequency/voltage.(you can use the app of your choice here).
3. set cpu and stability test to test the stability of CPU.
4. Some patience.
Step 1:
Set the current clock you want to test via any tool. (Select max frequency in cpu tab).
Step 2:
Open set cpu's cpu stress test and run it for atleast 10 minutes. If you didnt get any errors on those 10 minutes and the test completed successfully then the clock is ready for daily use
Step 3:
Now for undervolting use the same tools and reduce the voltage by -25mv.
Repeat step 2.
you can reduce the voltage further by -25 mv after the completion of stress test until the app become unstable. (Advanced users can try reducing -50mv )
Step 4:
Repeat step 1,2 and 3 for every possible cpu clock you see in tools.
Note the stable cpu voltage for every clock, once you finish testing all your clock values save it as a profile in nstools and set it on boot.
Voila !!! now you have finished overclocking/ under voting your beast The very same guide can be used to underclock you cpu.
Notes:
1. Not all chips are capable of running at higher speeds like 1800 mhz. Those speeds are highly experimental.
2. Recomended max overclocking is 1600 mhz.
3. If your device gets hotter allow the device to cool for few minutes before starting the test.
4. Combining the overclocking and undervolting will give you the best of both the worlds.
Overclocking GPU
Simple: Gpu oc is the same as Cpu oc : higher is the frequency, higher is the power consumption there are several frequencies in the kernel :
On stock kernel there's only the gpu 3d freq scaling :
3D freq:
266 mhz
228 mhz
200 mhz
2D : 200 mhz only for core 0 and 1 ( there are 2 2D cores and 1 3D core)
On custom kernel, there is the gpu oc, that add some freq for 2D and 3D
3D : 300 and 320 mhz
2D : 228 and 266 mhz
In some kernel ( Forzaferrarileo and Novakernel)
There's also the 2D freq scaling
So in custom kernel with gpu 2D/3D scaling the freq are these :
3D
160 mhz (in some kernel)
200
228
266
300
320
Those are the common freq for 2D. If the kernel doesn't have 2D scaling , only one freq is used. else all the frequencies can be used.
Thanks Forzaferrarileo
Great Thread !!:highfive:
Sticky it !!
Great info Harsh... Thanks a lot... I second that, this should be a sticky.
Sent from my Xperia S using xda app-developers app
Could you explain fiops and sakuractive as well.
Tnx
Sent from my LT26i using Tapatalk 2
Can you please credit to the owner that make this?
I think I have saw this in Xperia mini,mini pro,Live with Walkman,and Active community...
**deleted **
funky0308 said:
Could you explain fiops and sakuractive as well.
Tnx
Sent from my LT26i using Tapatalk 2
Click to expand...
Click to collapse
yea incoming soon !!
UchihaDareNial said:
I think I have saw this in Xperia mini,mini pro,Live with Walkman,and Active community...
Click to expand...
Click to collapse
no chance mate, i have not even COPIED it from any xda thread, and i don't even know if the above community exsists..
I found this all at various sites on nte like droidforum and rootzwiki etc.. and not a single thread is copied entirely !! various parts are joint together
Hope m not offending anyone !!
Updated with info about sakuractive and FIOPS.. Very limited info is found about FIOPS, tried my best to gather information.. Would keep it updated !!
-Harsh- said:
yea incoming soon !!
no chance mate, i have not even COPIED it from any xda thread, and i don't even know if the above community exsists..
I found this all at various sites on nte like droidforum and rootzwiki etc.. and not a single thread is copied entirely !! various parts are joint together
Hope m not offending anyone !!
Click to expand...
Click to collapse
Ohh I see...well,if that so,nice job
Sent from my LT28h using xda premium
Searching for a long time.. Finally got it.. U r awesome brotha... Going to study it now.... Hope i can understand all...
Stock Xperia S With Some MoD
rajeevxperia said:
Searching for a long time.. Finally got it.. U r awesome brotha... Going to study it now.... Hope i can understand all...
Stock Xperia S With Some MoD
Click to expand...
Click to collapse
I also feel good that i could be useful to such a helpful community of XS..
Sent From The Beast - Nexus 10
-Harsh- said:
I also feel good that i could be useful to such a helpful community of XS..
Sent From The Beast - Nexus 10
Click to expand...
Click to collapse
You, my man, doing a great job, just keep on going :thumbup:
Sent from my LT26i using Tapatalk 2
I am confuse in selection of Rom .can any one suggest me .I want to increase my battery performance .should I use xzxperience2????
Sent from my LT26i using xda app-developers app
ksbz said:
I am confuse in selection of Rom .can any one suggest me .I want to increase my battery performance .should I use xzxperience2????
Sent from my LT26i using xda app-developers app
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Click to collapse
Try cm10.1/pac/slimbean with beta 2 kernel and sakuractive-fiops combination for better battery life.
Sent from my Xperia S using xda premium
This is awesome man!
Sent from my One S using xda app-developers app
Thanks for this useful post - now i can understand what the devs of various ROMs and kernels are talking about.
Updated second post with info on GPU overclocking !
-Harsh- said:
Updated second post with info on GPU overclocking !
Click to expand...
Click to collapse
thanks a ton !!
Epic! Thanks!
Which ROM,governor and scheduler are you using currently?
Sent from my Xperia S using xda app-developers app