[Galaxy S6 / S6 Edge Unified Development] Xileforce:
FAQ's

1. What Is VControl And How Do I Use It?:

VControl is a kernel tweaking "app" built into the ramdisk. It is accessed via terminal emulator. To use it simply download terminal emulator, Type "su" without quotes and hit enter. Grant terminal emulator super user permission and then type "VControl" without quotes. Please note that it is case sensitive. This will bring up a text menu and you navigate by simply entering the option number you want and hitting enter. It is currently a WIP. More will be added to VControl over time.

2. You Broke My Phone! Fix It!:

It will be quite hard for me to figure out what is going on if you don't provide details and a log of what happened. To get a log use any file manager with root support and navigate to proc/last_kmsg.

3. What Kernel Tweaking App Should I Use?:

To Tweak the kernel, currently the only apps that work well are Kernel adiutor and Kernel toolkit as well as synapse. You can also use VControl for a limited number of things. Synapse is now built into the kernel so simply install the app.

4. What Do Power Efficient Workqueues Do?:

Typically when a task is created, it is bound to the cpu it was created on. This is great for performance due to maintaining cache locality. However its not the best for battery life. Power efficient workqueues attempts to schedule tasks on already awake cpus. A quick note about awake and sleeping cpus. A sleeping cpu doesnt mean the cpu is turned off or not hotplugged, nor does this mean it has to be deep sleeping. A core can be online and still be sleeping which means it uses very little power. This is why we are able to run with all 8 cores on all the time. Most of the time the majority of the cpus are sleeping. With power efficient workqueues, jobs will attempt to schedule on awake cpus which means we dont have to wake up the cpus that are sleeping already. This means we lose cache locality so we suffer a small (very small) performance hit but we potentially save noticeable amounts of battery. Enable for battery, disable if you plan on benchmarking or just want the extra power. They are off by default.

5. What Is Strict Aliasing And Why Should I Care?:

One of the big things Linaro does with improving Android's performance is fixing violations of what's known as "the strict aliasing rule." A pointer is said to alias another pointer when they both refer to the same location of memory. This is OK and not an uncommon thing to do. The strict aliasing rule is that pointers of different types should never refer to the same location of memory (aka alias each other). Strict aliasing allows a compiler to make some assumptions when compiling and optimizing code that it otherwise couldn't. It's actually one of the biggest optimizations you can do and it is fairly hard to add which is why most people don't. Here's a nice read up on it http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html#benefits

6. What does Small CPU Task Packing Mean?:

Task packing Is a process done by the scheduler. What it tries to do is pack all tasks onto as few cores as possible. In this case, it only packs tasks for the low power(small) cores as we want to maintain maximum performance and spread the load out on the bigger cores. The advantage of packing tasks is that if we envision a scenario where there is a 40% load and that gets spread out across the 4 small CPUs at 10% load each all 4 small CPUs are awake and running at a low frequency. With task packing all 40% would be shoved onto 1 core and the other 3 would sleep. This provides energy savings. However there becomes a point where the frequency required to process the extra tasks becomes high enough that it would use less power to run two cores at half the speed rather than 1 core at a very high speed. In this scenario the scheduler will automatically let tasks spill over onto adjacent CPUs in order to maximize power efficiency. One down side to this is a small performance hit due to having to pull the other cores out of a sleep state in the event of needing immediate power. However I would guess most people couldn't notice a difference.

7. What is power aware scheduling?:

Power aware scheduling is a method of scheduling where we make the scheduler aware of the actual efficiency of the cores. As you know, the small cores are more efficient than the big cores. The existing method for scheduling work uses a more basic (if the load is above this point, then move it to the big cores) type of decision making. With power aware scheduling, the scheduler will schedule tasks based on its knowledge of the cores power efficiency. Typically this reduces performance, though it's likely not noticeable except for in some games. If you want more battery, enable this. If you want more performance or have lag in games disable.

More will be added as they come up and I think of them.