Android Overclocking, Governors and IO Schedulers?? ~ Android Coliseum

Android Overclocking, Governors and IO Schedulers??

What does all this mumbo jumbo mean. Do I need it? What can it do? What can't it do? Are all valid questions that most people dabbling in the Android smartphone world have eventually.

Let's first start with the fact that you need to be ROOTED to be able to change any of those properties. This possibly eliminates half of the Android users out there.

This isn't a tutorial, this is just to explain to those who are asking the questions about it because they are rooted, they see the options but aren't sure what is what.

I personally don't overclock my devices and that's just because now we have quad core smartphones or tablets that are able to deliver. You always runt he risk of damaging your device if you do. Granted most chip have built in power off when it reaches dangerous levels, but that doesn't mean you should just go ahead and do it.

I'll focus mostly on what can actually increase the performance of your device. There's no guarantee that it will not adversely affect it.

Governors and IO Schedulers what are they? A short and simple answer; they affect how your processor (CPU), video processing (GPU) and your flash memory access. All 3 components are intertwined and work together.

If your interested to have more in depth information you can refer yourselves to the CPUfreq Governors guide at

I will focus on the main Governors and IO Schedulers offered on Android and I know this might not cover all the different ones.

Since a lot of the information has been provided already I will take extracts from and in a simple form.


1: OnDemand Governor:


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. Because users are vastly more likely to complain about performance than they are the few hours of extra battery life another governor could have granted them. But then again you'll get people who will complain about both.


2: Performance Governor:


3: Powersave Governor:

The opposite of the Performance governor, the Powersave governor locks the CPU frequency at the lowest frequency set by the user. Prepare for slow performance and slow reaction time.

4:Conservative Governor:



5: Interactive Governor:





There you have it for governors. These are the most often used ones. Now depending the kernel you may have on your phone or the one you've flashed you may have additional options.

I/O Schedulers

Based on two facts:

Disk seeks are really slow.


Read requests from processes are never starved.
As good as noop for read-performance on flash drives.

‘Guess works’ might not be always reliable.
Reduced write-performance on high performance disks.


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.

Believed to be very good for usb data transfer rate.
Considered an accurate i/o scheduler.
Achieves about 30% more throughput than CFQ on most workloads.

Not the best scheduler for benchmarking.


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.

Considered to deliver a balanced i/o performance.
Easiest to tune.
Excels on multiprocessor systems.
Best database system performance after deadline.

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.



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.




Best for flash drives since there is no seeking penalty.
Good throughput on db systems.



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

Simple, so reliable.
Minimized starvation of requests.

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


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.

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

Performance fluctuation results in below-average performance at times.
Least reliable/most unstable.

In the end of you have questions feel free to reach out to me. I'll be more then happy to help you out.
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