arter97 kernel for OnePlus 9 series running OxygenOS
/* Features */
Supports OnePlus 9 series
Fully rebased kernel without unnecessary OnePlus code
Latest CAF msm-5.4 kernel fully merged
Latest Linux v5.4 subversion merged
Latest Google’s security fix merged
BBR as the default TCP network congestion control
Features the latest WireGuard
Modules support disabled for lighter kernel
Latest Wi-Fi drivers from Qualcomm with customized config
Built with Clang 13 and ThinLTO
Memory management optimizations
Latest SELinux subsystem backported from mainline
Latest f2fs backported from mainline
Latest BFQ I/O scheduler backported from mainline
mmap/mremap backported from mainline for a major performance boost
Touchscreen optimizations for lower latency
Uses LRNG for better performance
/* Details */
- Fully rebased kernel without unnecessary OnePlus code -
This kernel is not based on the stock OxygenOS kernel source provided by OnePlus. Instead, it’s based on the latest and greatest Qualcomm has to offer. Only the necessary parts from the OnePlus kernel have been cherry-picked, such as OnePlus 9 specific device drivers.
This effectively kills all kernel modifications/optimizations from OnePlus, including the infamous app throttler.
Due to the completely different base, this kernel will behave drastically different from other kernels, in both good and bad ways.
- Power optimizations -
This kernel makes some conscious decisions for reducing power consumption.
First, the stock OnePlus configuration forces display-related processes to use the big cores exclusively.
This configuration brings a huge power regression since it makes every frame dispatch to wake up and use the power-hungry cores.
This kernel allows these processes to use little and middle cores (0-6), depending on the load.
Second, this kernel disables wakelocks upon Wi-Fi’s RX unicast packet transmissions. qcom_rx_wakelock is one of the major culprits to increased idle power consumption. Although its total wakelock time is quite low, it's catched very frequently and prevents the system from entering suspend repeatedly.
As dropping unicast or local ARP packets doesn’t pose practical issues on Android, this kernel disables qcom_rx_wakelock.
Third, this kernel reduces the duration of the Bluetooth ISR wakelock from 2 seconds to 100ms. This was done from an observation that the average userspace response time from ISR is less than 10ms.
My kernels have been doing this for years and no Bluetooth-related issues were reported.
Fourth, the vibrator driver used in this kernel no longer controls the cpuidle driver. The stock kernel disables the cpuidle whenever the vibrator is used. This kernel disables it as the vibrator is not that sensitive to deadline misses.
There are other small improvements throughout the kernel tree as well.
- Memory management optimizations -
This kernel marks the first Linux v5.4 based Android kernel to have MGLRU backported.
MGLRU is a big deal in everything Linux related, especially for Android.
Esper have a great article on what is MGLRU in a nutshell: https://blog.esper.io/android-dessert-bites-22-linux-memory-management-38419756/
According to Google’s fleetwide profiling, multi-generational LRU yields an “overall 40% decrease in kswapd [the kernel daemon that manages virtual memory] CPU usage,” an “85% decrease in the number of low-memory kills at the 75th percentile,” and an “18% decrease in app launch times at the 50th percentile.”
This kernel also disables LMKD and uses an in-kernel solution called SimpleLMK, made by kerneltoast. You can track how often SimpleLMK kicks in by monitoring:
This kernel also changes a lot related to swap and zram.
The swap-related code has been backported from Linux v5.9 (link1, link2) to efficiently support fast swap device and allow swappiness over 100. This kernel currently sets swappiness to 160 on < 6GB of RAM, 120 on 8GB and 90 on 12GB.
zram has been also backported from mainline Linux
This kernel uses zram writeback to offload idle pages (i.e., really, really unused RAM) to the internal storage. As it's extremely slow to bring pages back from UFS, writeback code works quite conservatively. It'll start to writeback pages that haven't been used for a day or two. It makes use of the hidden 2GB “last_parti” partition from the UFS storage.
Along with zram writeback,
zram writeback is temporarily disabled to avoid lags on long uptime with r20.
The post boot script used in the stock ROM is also overridden and it sets the readahead to 128KB. As I/O workload under Android is mostly random, high readahead doesn’t help and only increases memory thrashing.
This kernel also incorporates a lot of patches to reduce/optimize memory allocations used throughout the entire kernel.
mmap/mremap code was also backported from Linux v5.10 to optimize ART (see here for more info).
- Latest subsystems -
This kernel backports the SELinux subsystem from mainline Linux. This includes caching improvements that drastically reduces time spent on lookups. 10K lines of code has been changed.
This kernel also backports f2fs (Flash-Friendly File System) from mainline Linux. This includes bug fixes and performance improvements such as shorter discard latency, more optimized GC logic for Android, and checkpoint merging.
BFQ I/O scheduler has also been backported from mainline Linux for better I/O performance.
- LRNG -
/* Notice */
OxygenOS 12 is unsupported.
Non-OxygenOS custom ROMs are supported, but your mileage may vary wildly. Most notably, gesture orientations on some ROMs may be inverted.
Custom ROMs that uses OxygenOS 12 kernel, including LineageOS 19.1, are not supported.
This kernel touches vendor_boot and dtbo partitions, meaning you'd need to restore said partitions whenever you're switching to another kernel or stock.
Please make a back-up of these partitions. The installer doesn’t do this automatically for you. Installing the stock ROM with a full OTA restores said partitions as well.
/* Disclaimer */
Your warranty is now void.
I am not responsible for bricked devices, dead SD cards,
thermonuclear war, or you getting fired because the alarm app failed. Please
do some research if you have any concerns about features included in this kernel
before flashing it! YOU are choosing to make these modifications, and if
you point the finger at me for messing up your device, I will laugh at you. Hard. A lot.
/* Thanks to */
/* Instructions */
1. Read the above. Please.
2. Flash the zip file from FK Kernel Manager. Any other installation methods are untested.
/* Downloads and links */
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