Explanation on Governors & I/O schedulers :
Read the below links for everything
http://xdaforums.com/showthread.php?t=1767797 ( All governors & schedulers explained )
http://xdaforums.com/showthread.php?t=2301294 ( All governors & schedulers explained )
For people who are lazy i have put through some here
Performance governor helps gaming according to people who tried my kernel in A250. I can't confirm the same here since i am not a gamer. So try that for gaming and let people know.
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.
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
ZZmoove
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.
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.
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.
I/O Schedulers :
I/O Schedulers Explained
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.
