What is Governor CPU, I / O scheduler and how they affect the Android device?

In the process of using Android, especially those that you have deep rooting and inversely to the system, you must also faintly seen through the word "CPU Governor" and "I / O scheduler". I, too, and before I did not care what it is because of the people that put their available, use it. However, the time to learn about the tools refine the system ROM Toolbox app, I see Governor CPU and I / O scheduler should account for two huge new item questions. So I began to learn more and found out that these are two very interesting things in Android. Today I would like to share with you about them.

1. What is CPU Governor?

A "governor" (roughly translated: rulers, the leader, the head ") is a component used to control the cpufreq, ie the CPU clock. Governor's mission is control CPU clock speed increase or decrease for suit the user's needs. Governor crucial for smartphones and tabet because it greatly affects the smooth interface and battery life of the device you are holding in your hands.

Governor has a lot of CPU, the kind designed for dual-core processors, there's just one kind, but also quad-core type for another. To switch between the Governor with each other, and equipment required to root your right, and you must own a ROM or a software that has the ability to change the Governor. It should be noted that each of the different kernel (kernel middleware is standing between the hardware and the operating system) is usually accompanied by a set of different governor jog.

Some software can be used to change CPU Governor:
1. SetCPU.
2. No-frills CPU.
3. Tegrak Overclock.
4. ROM Toolbox

In the following article, I will illustrate it with SetCPU software familiar supported by this app tweak many things, including governor and overclocked CPU and the interface is very simple. In the main interface of this app, you will see the current pulse is shown by the largest number in the middle, governor displayed just below it and beneath that is the I / O scheduler (which we will find understand later). Two blue numbers that you can tweak it, it allows you to set the maximum and minimum pulse device. Peering down again you will see the option governor.


Following are details of some popular governor:

1. ondemand: ondemand you can find in most Android kernel and is usually much default kernel governor. When the CPU load reaches a peak (up threshold - you can adjust this in the "Governor" - drag your finger to the right twice), ondemand will rapidly increase to the highest CPU clock is able to meet the demand for our machine, then it will gradually reduce the pulse down. When set ondemand, I realized that in most cases, the machine will push up to the maximum CPU clock by setting themselves. When the task is completed, pulses will be reduced. Continuing to run something else, the CPU is pushed up and this happens a lot if you often use many apps at once (multitasking)

ondemand governor is one of the manufacturers chosen because it works stable and thoroughly tested to ensure the best performance for the smartphone. Although not save battery as some other governor, but it does not affect much. Enjoy subjects using a slow machine, jerk than being reduced by about 2-3 hours battery life but have good texture, you choose?

2. interactive: Governor can also be easily found in the kernel and a lot of manufacturers are usually selected as the default device. interactive functions similar to ondemand, but it focuses more on increasing the reaction rate of the CPU speed changes.

If the pulse ondemand tweaking depending on the task to be "in line" waiting for their turn, the interactive adjustment by a timer pulse (timer) with the given time. The timing is determined by the kernel programmers write. In other words, if an application requires 100% CPU load, users still have enough time to run a different task before starting off CPU clock if programmer put long enough period of time. Also thanks to the interactive timing that can make better use of the clock in the middle of the maximum, minimum. (For example, a 1500MHz max, min is 300MHz, you will see the machine running at 1000MHz, 800MHz, 700MHz, 600MHz, ...)


However, because interactive is allowed to spend more time in clocked up more than ondemand (for the purposes of improving performance), so it may be a negative impact to battery life. Although so, in most case, interactive will for high performance more than, longer difference time used pin not too large.

In addition, interactive also assume that when the user opens the screen up, they will quickly interact with applications on the machine. Thus, the opening screen will make CPU clock up to a maximum, and then when you run the app, the pulse is still at maximum.

3. conservative: some presence in the kernel and it also works almost the same way with ondemand, however, increase the CPU clock speed is not as fast as ondemand, so that it will better meet the needs. conservative was created with the aim to keep the machine running at a minimum clock often as possible. Depending on how developers set parameters for governor, as well as minimum clock select which computer users will have different performance. In general, conservative making device we become less sensitive than ondemand. In return, you will have longer battery life longer.

4. performance: There face in most of the kernel. Governor will keep the CPU running at clock up everywhere. Compared to using ondemand and set the pulse maximum and minimum of the same value, performance brings greater efficiency. As its name suggests, the chosen Governor of this, our machine will operate with the highest performance possible, promote the full power of the CPU, but will drain the battery more.

The establishment for machine always run in pulse rhythm default listening to have sound crazy, but actually substances also have reasonable own. Because the CPU is always active with good speed multi so it will "run to" faster. The process "run about purpose" this been community hardware called is race-to-nghỉ. Race-to-nghỉ is the process which phone completed a assigned work (for example such as synchronous email) and then returned about status extremely power saving of CPU.

5. powersave: Available in some kernels. It will keep the CPU always runs at minimum speed that the user set up, so battery life will be extended, but it will slow to clear. Immediately both pcs Nexus 4 famous smoother but when adjust governor into powersave with lowest level then you will have the feeling want ... beat machine.

6. hotplug: Only available in some ROM support for multi-core processors. It is similar to the ondemand, but it will turn off the excess away when not needed.

7. userspace: According to SetCPU, the Governor must be used with a method to control CPU clock not SetCPU. Developer this app recommend we should not select userspace governor. Indeed userspace uncommon on the phone, mostly used on desktops and servers to allow the application to run by authorized users tweak clock.

8. smartass: Usually found in the ROM custom, ROM Cook. smartass governor will keep machine running at pulse rhythm lowest in case devices're in status salvation. Indeed Governor uses the same idea with Governor interactive, but the performance is worth the price is on par with Governor min max, while the battery is also raised slightly because most of the time the smartass is running at clock low .

Apart out, smartass adjust pulse rhythm maximum in sleep mode about 352MHz. Even if you set the min frequency is higher than 352MHz, it is still dragging on. Therefore, you will not need to sleep anymore profile.

9. min max: Depending according degree of download of CPU which machine will run or in pulse rhythm highest, or in pulse rhythm lowest, not have certain clock in between.

10. scary: a Governor recently wrote based on conservative but has a number of features of smartass. It will start at the lowest speed, take a sample and if the models need higher speeds upthreshold, scary increase pulse rate every time a level (at reduced too). Top speed off when the screen is 245MHz and most of the time, scary will run at clock low. The goal of scary, in a nutshell, is to achieve battery life good for performance average.

SetCPU, XDA