The document discusses approaches to reduce boot times for ARM Linux devices by implementing technologies like rloader and hibernation. It highlights key methods for measuring boot time, optimizing bootloader processes, and different software hibernation technologies. The content is aimed at improving user experiences in various devices including smartphones and tablets, illustrating challenges and potential solutions.

1. Connect your device to application

2. Rloader,
Alternative technology to
achieve fast boot time
for ARM Linux
Matt Hsu
<matt@0xlab.org>

3. Agenda Motivation
Boot Time Measurement
Reduction Approach
Hibernation Based Technologies
Rloader
Demo
Summary
Q&A

4. Movitation

5. Why Boot Time?
Define boot time, please
Power saving
User experiences
Android's boot time is especially painful
Devices
Tablet
In-vechile system
TV
Smart Phone
Camera

6. We Are Not Alone
Quick boot
Ubiqutous
Improving meego boot-up time
Hiroshi DOYU, Nokia Sotware Architect
Boosting up embedded Linux device: experience on
Linux-based smarphone
Samsung Electronics Co. Ltd.
Swap-before-hibernate: A fast-on algorithm at OS
level
Shi-wu Lo, OS Lab, CCU

7. Embedd Linux Wiki

8. Boot Time Measurement

9. Kernel space
Kernel parameter
printk.time =1
linux-2.6/scripts/show_delta
Ftrace
ftrace=initcall
Initcall
Enable BOOT_TRACER config
./scripts/bootgraph.pl boot_time >out.svg
initcall_debug

10. User Space
Bootchart
http://www.bootchart.org/
cat /proc/uptime
2012.39 512.64
grabserial
http://elinux.org/Grabserial

11. Hardware Approach
External instrument
Scope
Logic Analyzer
Hardware timer count
Resolution is dependent on your clock source
ETM (Embedded Trace Microcell)
Need assisted software such as TRACE32/OpenOCD
New feature in ARM Cortex seies

12. Reduction Approach

13. Divide and Conquer
Bootloader
Kernel
Userland

14. Bootloader
Minimal bootloader
Qi bootloader
zboot, linux boot directly
Enable I-cache
Copy kernel into base + 0x2000000 offset
DMA-capable copy
Multi-block read (MMC)

15. Kernel
Kernel parameter
quiet
Preset LPJ
Loop per jiffy
Deferred initcall
include/linux/init.h
arch/arm/kernel/vmlinux.lds
Compressed kernel
UCL
XZ

16. Userland
Optimize linker and loader time
Specific linker option
Parallelize rc script
Application specific optimization
Hibernation based technologies

17. Hibernate-Based Technologies
Swsusp, aka software suspend
Swsusp2 (TuxOnICE)

18. Swsusp
Natviely support in x86
Based on work by
TI, Teerth Reddy
https://patchwork.kernel.org/patc
h/96442/
Nokia, Hiroshi DOYU
https://lists.linux-
foundation.org/pipermail/linux-
pm/2010-June/027422.html
Start hibernation
echo disk >/sys/power/state

19. Swsusp2/TuxOnICE
Not support in main line
kernel
Provides many features
Compression of images
Readhead
multiple thread I/O
drop pagecache
Hbernation trigger
eho 1
>/sys/power/tuxonice/do_hib
ernation

20. Rloader, (Resume Loader)

21. Rloader Is Nothing New
Do we really need follow normal booting process?
The implementation of Rloader could be
Bootloader
snapshot boot
www.elinux.org/images/3/37/Snapshot-boot-final.pdf
Custom kernel
Kernel with software resume support
Different hibernation images make difference user scenario

22. Booting Process
Normal booting
Boottloader
Kernel Init init.rc, platform-specific rc
init
Kernel as Rloader
Bootloader Minimal device Restore
init Init process
Bootloader as Rloader
Bootloader Restore
init process

23. Make ARM Hibernated
Merge patches
swsusp patch from TI/Nokia
TOI patches according to your kernel version
'swap out' page as much as possible
ARM does not support ACPI
Currently, there are patches for ARM
Cortex A8/A9 provided

24. Hardware/Software Descripton
ARM OMAP3 Beagleboard
Kernel
2.6.32 with corresponding TOI
patch
Bootloader
Qi
256MB RAM
0xdroid Eclair

25. Something before hibernating
echo 100 > /proc/sys/vm/swappiness
echo -2 > /sys/power/tuxonice/image_size_limit
echo 3 >/proc/sys/vm/drop_caches
busybox swapon -p 1 /dev/block/mtdX

26. Normal Booting Time Diagram
25 seconds
GPIO signal of
Key-guard event
GPIO signal of
Power On Reset stepping into kernel

27. Hibernation Boot Time Diagram
6 seconds
Power On Reset GPIO signal of GPIO signal of
stepping into kernel Key-gurad event

28. Rloader as Kernel or Bootloader?
It's a trade-off between your boot time and
management cost
Maintainence
Once kernel/TOI changes, you need to re-implement
Complexicity
How to restore pages?
Resume point? PC value?
Improved room might be limited

29. Further Optimization
Re-construct initcall stages
Try different algorithm out on compressing
images
http://code.google.com/p/snappy/
Lazy loading
Put driver state into hibernation image

30. Summary
It's still far away from being a product
File system inconstency
Power failure as hibernation
Hardware solution is the sliver bullet?
The time of stepping into hibernation is also
needed to concern

31. Demo

32. Resource
http://elinux.org/Boot_Time
http://tuxonice.net/
http://gitorious.org/improving-meego-boot-up-time/t2t/commit/d29d8576cf7
www.kernel.org/doc/ols/2010/ols2010-pages-9-18.pdf
http://gitorious.org/+0xlab/0xlab-bootloader/qi-bootloader
http://www.oberhumer.com/opensource/ucl/
http://code.google.com/p/0xdroid/
www.kernel.org/doc/ols/2010/ols2010-pages-9-18.pdf

34. Sponsored
by
http://0xlab.org
27 May 2011