¤ OOM groupings :
Android, like any other Linux system, has a built-in task killer, called the LowMemoryKiller (a.k.a LMK).
The LMK analyses the RAM usage of all applications in real-time, and when the system has too many apps open, or too much RAM consumption, the LMK will start killing apps to free-up some memory.
To determine which app to kill first, the LowMemoryKiller distinguishes 10 categories of apps, which are called the
Out-Of-Memory (OOM) Priorities.
As the name implies, the LMK will create a kind of ordered list based on the determined priority of the apps.
Those categories are as follow :
- Foreground App
- Visible App
- Secondary Server
- Backup App
- Home App
- Hidden app
- Empty App
- Perceptible App
- Heavy-Weight App
- Content Provider App
For each of these categories, Pimp my Rom will modify the memory threshold for LMK to start killing processes and adjust the priority of the categories to match three preset levels of multitasking :
- Low : Your device will be able to handle less opened apps at once, but consume less RAM and less battery
- Mid : An average good level of both Multitasking and not too much RAM drain/Battery drain
- High : Your device will be able to handle a big bunch of opened apps at once without being killed
The OOM settings in PmR also takes care of the ADJ, but I might add a separate 3 levels radiogroup for ADJ too
¤ Minfree Values :
The LowMemoryKiller isn't only about OOM groupings, the Minfree values are very important as well :
The Minfree module of the Low Memory Killer is here to set the minimum amount of free RAM that should always be available.
If the free RAM level goes below the Minfree value, the the LMK starts killing apps (based on the OOM priorities, remember ?
)
In other terms, if the LMK is the gun for killing apps, then the Minfree module is the trigger ^^
Again, PmR will allow you to choose between 3 preset levels (for the purpose of clarity for the user, the levels are inverted from the actual values. i.e : High Level in the app wil set a low minfree value, allowing for more multitasking) :
- Low : The minimum amount of free Ram (minfree) will be set high, allowing apps to get killed by the LMK quickly. = Not much multitasking, but good battery/less lags as you always have a good amount of free ram
- Mid : Balanced Level, good multitasking, not much lags and average battery
- High : Big multitasking hog
¤ zRam (Zero Capacitor Ram) :
Taken from Wikipedia :
zRam is an experimental (staging) module of the Linux kernel. It was previously called "compcache". zRam increases performance by avoiding paging on disk and instead uses a compressed block device in RAM in which paging takes place until it is necessary to use the swap space on the hard disk drive. Since using RAM is faster than using disks, zRam allows Linux to make more use of RAM when swapping/paging is required, especially on older computers with less RAM installed.
To make it simple, zRam allows to virtually increase the amount of RAM your device has by using the Swap spaces in your device memory.
This is mostly profitable for low-end devices that come with few ram (512mb generally).
PmR offers 2 levels :
- 64 mb : virtually adds 64mb of RAM
- 128mb : virtually adds 128mb of RAM
zRam settings requires a kernel that includes this module.
I hope these little explanations will help you understand how to use those settings, and help you find the right combination for your device and use
