Android for IVI Android for IVI: overcoming enormous boot time

Transcription

1 Android for IVI Android for IVI: overcoming enormous boot time Vitaly Wool, BroLab AB

2 IVI In-Vehicle Infotainment Rear-seat entertainment Navigation and location-based services FM Radio, CD/DVD, mp3 Connectivity for mobile devices Call services

3 IVI and technologies GUI Display and touchscreen Video acceleration Connectivity Audio Bluetooth Wi-Fi USB

4 Android OS targeting primarily mobile devices Rich multimedia and connectivity functionality Used on hundreds of millions mobile phones Thousands of applications Ease of application development

5 Android for IVI? + Supports necessary hardware + Has required software libraries and applications + Easily extendable and customizable + Fast time-to-market - Resource demanding - Unacceptable boot times

6 Android boot times Very long Depend on the CPU frequency Depend on the number of cores Depend on the RAM amount GB ICS 0 1,4 GHz single core 1,5 GHz dual-core 1 GHz single core 1 GHz dual-core

7 Reducing Android boot time Readahead Prefetch data into page cache Parallelization Fine tuning See Tim Bird's ABS'2011 preso Start as many boot-time applications as services as possible Tracing and improving long operations Warm boot instead of cold boot ( Fastboot ) Suspend instead of power-off

8 Suspend-to-RAM Operation Features Stops all the devices Saves CPU state Puts RAM into self refresh and powers off CPU Full resume normally takes less or about 0.5 s Implemented and stabilized long time ago Consumes power while suspended The amount mostly depends on RAM size

9 Hibernation (suspend-to-disk) Operation Basically the same as for S2R Features RAM is dumped to the disk / flash memory Full resume takes 2-3 seconds Not that mature and used somewhat rarely Does not consume power in hibernated state

10 Hibernation and flash storage Hibernation includes writing massive portions of data to flash Takes time to complete (several seconds) May have to be thrown out if ECC fails Back to cold boot and long boot time Causes fast wear-out of the swap partition

11 Hibernation and wear-out Swap partition wear-out Case study Results obtained using nandsim with bad block emulation capability JFFS2, months YAFFS, months UBIFS, months 0 2 starts / day 3 starts / day 4 starts / day Emulating MLC

12 Android boot-time spenders Kernel is not a big spender Spenders Classes preloading Package scanning 85+% of the boot time will go away with fast boot from hibernation Kernel init system server zygote Java services

13 Re-use hibernation image? What if we start off with a pre-created hibernation image each time? fixes most of the Android boot time spendings Does not require excessive flash usage Microsoft did something similar (HORM) Problems Who will create this image? When should it be flashed?

14 Factory flashed hibernation? Suppose we can flash hibernation image in the factory One generic image for all Well tested No ordinary hibernation drawbacks Android can be optimized to work with it How can we do it? Hint: Android includes emulator :-)

15 Hibernation image creation Run normal Android build Filesystem images are ready Android emulator is built Launch Android emulator Classes are preloaded Package are scanned Then goes hibernation image creation

16 Emulator tweaks to enable FFH Add a launch option to create hibernation image This will be run as a part of Android build Should go non-interactive No GUI initialization Add hibernation image creation functionality Should only start when all classes are preloaded Post-process the FFH image to create.img

17 FFH drawbacks/problems Image should be recreated if an application is installed Are we going to allow user initiated application installation at all? Otherwise can be done while servicing vehicle Image should be recreated on Android version upgrade Android cookie upgrade is a corner case for IVI Can be done while servicing as well

18 Conclusions Android can hardly be used in IVI as is Mainly due to the boot time constraints However, the idea is very appealing Android fits IVI in most of the other aspects Ordinary boot time optimization methods don't work that well for IVI We need some IVI-specific optimizations FFH looks very promising

19 Thanks for your attention! Questions? Ideas? Interested in the solution? Vitaly Wool