[Nexus 7 (2013) Original Android Development] trjlive:
Just wanted to share my recent experience with this kernel on my N7. I've been using it with stock OS/Kernel (rooted) since I got it early this year, and while it's been just fine for me, I recently got the urge to try a custom kernel. As I've used ElementalX kernels on my previous HTC One, I decided to give it a try on this device.

My first install proved disastrous for my battery life. I installed with no UV, OC, and just all default options in Aroma, just so I could get a baseline. Very poor battery life. So to make sure this wasn't being caused my anything I had installed or configured, I decided to document a baseline setup, and then an ElementalX setup, and compare results.

My baseline stock install is as follows:

Use TWRP 2.7.0.0 to completely wipe all partitions on device.

Using Fastboot, push stock Android KTU84P image to device (including boot, system, userdata).

Reboot into TWRP and do a factory reset.

Reboot device and start first-run setup.

Connect to my wifi network (latest Apple AirPort Extreme 5GHz network, device about 15 feet from router).

Do not set up Google account or any other accounts, to prevent any Google Services from doing background downloads.

Sideload Gsam Pro Battery Monitor app apk and open once so it can set itself up.

Then press home button back to home screen.

So this is a stock, virgin, clean installed device with one single third-party app (Gsam) installed. Battery is at 100% full charge. Leave the N7 on, screen goes to sleep, and let it sit for 24 hours on my desk. Come back to it 24 hours later, battery is at 92% (which I expected around 90%). Gsam shows the wifi as being the biggest battery consumption.

Ok, so now to do an ElementalX baseline. I repeated the previous steps to get a clean, virgin installed system again, just to have the same exact baseline to start with.

Repeat all steps listed above for baseline stock install.

Then reboot device into Recovery, and install ElementalX-N7-2.13.zip.

These are the install options I chose:

Set each CPU core separately: No

CPU optimization level: elementalx

Thermal throttling: default

Maximum CPU frequency: 1512MHz (stock)

Auto Undervolting: Stock

Maximum GPU frequency: 450MHz 400MHz (stock) *

GPU governor: Ondemand

I/O Scheduler: ROW (default)

Read-ahead buffer size: 512 (default)

Wake gestures support: Disable S2W/DT2W

Sweep2Sleep: Disabled (unchecked all 3 options)

Other Settings: Disable fsync

I then rebooted the device back into the OS, verified the new kernel was correctly showing in About Device, which it was. Then I left the device to sit 24 hours on my desk, just like before. Battery was at 100% full charge. Came back to it 24 hours later, and the battery was at 67%. I was expecting somewhere around 90% since it should basically be just about the same stock settings, but this was a significant battery drain. I looked at Gsam to see what was using the battery. The top item was "Kernel (Android OS)". CPU usage was shown at 3 hours 12 minutes, Keep Awake at 57 minutes.

So these two tests, which I very carefully ensured the devices were configured identically except for the ElementalX kernel, and the device positioned in the same location in my house, same conditions, and same duration, and the ElementalX kernel held my device awake and for some reason was running the CPU for over 3 hours, and drained 67% of my battery.

I have not tried tweaking the various settings in the kernel setup, my reason being that by installing with default, stock-like settings should render results very close to stock. The fact that ElementalX is causing a significant drain on my device, on a fresh, virgin, stock install, with no other apps or syncing or anything installed, points directly to something wrong with ElementalX. I can repeat these results 100% of the time, by following the exact steps detailed above.

I am by no means a kernel developer, though I am a web/database developer and am quite familiar with Android, I don't know the ins and outs of kernel development. I'm quite confused, frustrated, and disappointed that I cannot use this kernel on my device. I have gone back to a stock kernel and my battery life is excellent, which is the minimum I expect from this device. I shouldn't have to do a whole bunch of funny tweaks to things just to get a kernel's performance back up to stock standards.

I understand there are a lot of people who are using this without these issues. I really wish I could be one of them. I just don't know how much more "vanilla" I could make my device to take anything else out of the mix. I may come back to this kernel down the road, and see if my results improve. Or if anyone could advise where in my testing steps I could do something different to get better results. Keeping in mind, I do not wish to cripple the functionality of my device just to get decent battery life, since I don't have to do so with stock kernel.

Anyway, I'm open to any suggestions or feedback that might help.

Update: * Corrected typo on selected GPU frequency. I had mistakenly typed 450MHz, when I had in fact chosen the stock, which is 400MHz. Corrected above.