[Galaxy S II Android Development] Saber:
Troubleshooting

(Probably one of the most detailed troubleshooting guides for kernels on XDA)

Q: Why flash your kernel?

This applies to gustavo kernel in general. gustavo kernel is an aftermarket kernel (or custom kernel) that is designed to allow users to tweak their phone at the kernel or near-hardware level side of things. In other words, users get more fine-grained control over their phone, this includes overclocking, underclocking, changing behavior of CPU/GPU etc. Adjusting such settings isn't for the faint-hearted since there is soooo many things to understand, but you aren't required to understand all of the settings. Ultimately, if you want to improve your phone experience, try gustavo kernel! :)

Q:How do I flash your kernel?

A: You flash kernels like flashing roms, except you don't have to factory reset your phone. If you can't flash the kernel for some reason, you can either flash philz recovery then flash the kernel OR you can just make your own kernel .tar file and flash via ODIN by following this guide: http://xdaforums.com/galaxy-s2/development-derivatives/convert-kernel-zip-to-tar-t2994381

Q: Which kernel version build should I flash?

A: Flash the latest stable version if you want the most stable experience. Builds that have not been marked with 'Stable' are mostly stable, or haven't been tested enough to earn a stable tag. Either way, it's up to you which one you want to flash. Read the changelog for any important changes that might have occurred in a particular build.

Q: Wifi doesn't work after I flash this kernel

A: There are two main causes to this issue, either there is a problem with your:

- Partitions OR

- Permissions OR

- Gapps OR

- ROM OR

- Compatibility with your wifi hardware

Don't use a pit with modded preload! It will just cause issues with ROMs and Kernels. Use stock pit or use a pit with unmodded preload. Sometimes, the gapps package you flash somehow breaks compatibility with the kernel. You can fix this by flashing a different gapps (making sure to clean cache and dalvik). If you have permissions problem, you can fix this by repartitioning your internal sd card or by reflashing back to stock rom. Sometimes, the ROM doesn't fully support the wireless drivers in the kernel, this can be solved by flashing a different ROM or different kernel. But if your wifi hardware is not compatible (a way to tell this is when you have tried everything and failed), there is nothing you can do but reflash the rom or flash a different kernel.

Q: My battery life sucks after flashing this kernel!

A: Download and install Betterbatterystats and see what is the culprit to your problem. If it is kernel related, have you made sure you have wipe cache and dalvik and reset stweaks settings? If yes, it would be nice if you posted a logcat.

Q: Why do I get bootloops with this kernel?

A: If you were on a working version on gustavo kernel lollipop before, there is probably something wrong with the installation. If you are on a ROM that is not lollipop, you flash the wrong kernel! You need to flash the right kernel for your android version. Sometimes, bootloops can occur due to corruption of the kernel zip file (usually from bad download) or from corrupted partitions.

Q: What do all of the settings mean? They are all confusing!

A: Please note that gustavo kernel isn't for users who have just rooted their device. Before jumping into the custom kernel world, try playing around with other kernels first. Once you think you have some experience, read the stweaks/synapse beginners guide I made and then attempt to tweak the kernel using stweaks/synapse.

Q: How do I trim my partitions?

BEWARE: Make sure you have read all of the precautions before attempting to trim your partitions!

Q: My device is (hard) bricked after flashing your kernel!

A: Have you read all of the precautions before installing the kernel? You made the decision to flash the kernel and now you've stuffed up your phone.

Q: I get constant FCs after flashing your kernel!

A: Have you wiped your cache partition, dalvik cache and reset stweaks settings? If you've done all of these already, a logcat would be nice :)

Q: What's a good combination for CPU governor and I/O scheduler?

A: Have a look at the default settings, they are optimised for our phone :)

However, here are some settings I personally like:

1. Governor: HYPER/Ondemand I/O scheduler:SIO/SIO

2. Governor: PegasusQ/Nightmare I/O scheduler: SIO/SIO

3. Governor: NeoX/Ondemand I/O scheduler: SIO/SIO

4. Governor: Nightmare/Nightmare I/O scheduler: SIO/SIO

Q: What is a TCP algorithm?

A: Congestion control strategies (or algorithms) are used by TCP, the data transmission protocol used by many Internet applications. The main goal of a TCP algorithm is to avoid sending more data than the network is capable of transmitting, that is, to avoid causing network congestion.

Q: Why not use XYZ toolchain?

A: See this post

Q: What is UBER?