This repo contains the code written for ASAP: Fast Mobile Application Switch via Adaptive Prepaging (published in ATC'21). For more detail about the project, please refer to our paper.

This code is a patch of Google Pixel 4's Linux kernel. To test this code, you should

1. Dowload Pixel 4's kernel using repo
2. Patch the code in this repo
3. Compile the patched kernel image, then flash it to Google Pixel 4.

$ mkdir $WD && cd $WD
$ repo init -u https://android.googlesource.com/kernel/manifest -b android-msm-coral-4.14-android10
$ repo sync -j4

$ git clone https://github.com/SNU-ARC/atc21-asap-kernel.git

Update app_table_init() function in atc21-asap-kernel/src/asap/sysctl.c to match applications installed on your device.

$ cp atc21-asap-kernel/src/* $WD/private/msm-google/ -R 
$ cp atc21-asap-kernel/config/* $WD

Please refer to Android official guide.

To test ASAP, you need to write pid of the switching application to /proc/sys/vm/switch_target_pid and write non-zero integer to /proc/sys/vm/app_switch_start at the beginning of the switch, and /proc/sys/vm/app_switch_end at the end of the switch. For test purposes, you can maunally echo to these pseudo files to enable ASAP's functionalities before and after the application switch as follows.

echo $pid > /proc/sys/vm/switch_target_pid

echo 1 > /proc/sys/vm/app_switch_start
## do applicaiton switch e.g. using am start
echo 1 > /proc/sys/vm/app_switch_end

To implement this in Android framework, you need to add gluing codes to ActivityManager codes. Please refer to this example. In our prototype, there was no performance difference between the test using echo and the real implementation in Android framework.

Sam Son (sosson97@gmail.com)

Please cite the following paper if you use this code.

@inproceedings {273883,
author = {Sam Son and Seung Yul Lee and Yunho Jin and Jonghyun Bae and Jinkyu Jeong and Tae Jun Ham and Jae W. Lee and Hongil Yoon},
title = {{ASAP}: Fast Mobile Application Switch via Adaptive Prepaging},
booktitle = {2021 {USENIX} Annual Technical Conference ({USENIX} {ATC} 21)},
year = {2021},
isbn = {978-1-939133-23-6},
pages = {365--380},
url = {https://www.usenix.org/conference/atc21/presentation/son},
publisher = {{USENIX} Association},
month = jul,
}