Connect your device to application

Rloader,Alternative technology to achieve fast boot time for ARM Linux

Matt Hsu

<matt@0xlab.org>

Agenda Motivation

Boot Time Measurement

Reduction Approach

Hibernation Based Technologies

Rloader

Demo

Summary

Q & A

Movitation

Why Boot Time?Define boot time, please

Power saving

User experiences

Android's boot time is especially painful

DevicesTablet

In-vechile system

TV

Smart Phone

Camera

We Are Not AloneQuick boot

Ubiqutous

Improving meego boot-up timeHiroshi 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

Embedd Linux Wiki

Boot Time Measurement

Kernel spaceKernel parameter

printk.time =1

linux-2.6/scripts/show_delta

Ftraceftrace=initcall

InitcallEnable BOOT_TRACER config

./scripts/bootgraph.pl boot_time >out.svg

initcall_debug

User SpaceBootchart

http://www.bootchart.org/

cat /proc/uptime

2012.39 512.64

grabserialhttp://elinux.org/Grabserial

Hardware ApproachExternal instrument

Scope

Logic Analyzer

Hardware timer countResolution is dependent on your clock source

ETM (Embedded Trace Microcell)Need assisted software such as TRACE32/OpenOCD

New feature in ARM Cortex seies

Reduction Approach

Divide and Conquer

Bootloader

Kernel

Userland

Bootloader

Minimal bootloaderQi bootloader

zboot, linux boot directly

Enable I-cache

Copy kernel into base + 0x2000000 offset

DMA-capable copy

Multi-block read (MMC)

KernelKernel parameter

quiet

Preset LPJLoop per jiffy

Deferred initcallinclude/linux/init.h

arch/arm/kernel/vmlinux.lds

Compressed kernelUCL

XZ

Userland

Optimize linker and loader timeSpecific linker option

Parallelize rc script

Application specific optimization

Hibernation based technologies

Hibernate-Based Technologies

Swsusp, aka software suspend

Swsusp2 (TuxOnICE)

Swsusp Natviely support in x86

Based on work byTI, Teerth Reddy

https://patchwork.kernel.org/patch/96442/

Nokia, Hiroshi DOYUhttps://lists.linux-foundation.org/pipermail/linux-pm/2010-June/027422.html

Start hibernationecho disk >/sys/power/state

Swsusp2/TuxOnICENot support in main line kernel

Provides many featuresCompression of images

Readhead

multiple thread I/O

drop pagecache

Hbernation triggereho 1 >/sys/power/tuxonice/do_hibernation

Rloader, (Resume Loader)

Rloader Is Nothing NewDo we really need follow normal booting process?

The implementation of Rloader could beBootloader

snapshot boot

www.elinux.org/images/3/37/Snapshot-boot-final.pdf

Custom kernelKernel with software resume support

Different hibernation images make difference user scenario

Booting Process

Boottloaderinit

Kernel Init init.rc, platform-specific rc

Normal booting

Bootloaderinit

Minimal deviceInit

Restoreprocess

Bootloaderinit

Restoreprocess

Kernel as Rloader

Bootloader as Rloader

Make ARM Hibernated

Merge patchesswsusp 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

Hardware/Software Descripton

ARM OMAP3 Beagleboard

Kernel2.6.32 with corresponding TOI patch

BootloaderQi

256MB RAM

0xdroid Eclair

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

Normal Booting Time Diagram

Power On ResetGPIO signal of stepping into kernel

25 seconds

GPIO signal of Key-guard event

Hibernation Boot Time Diagram

GPIO signal of stepping into kernel

GPIO signal of Key-gurad event

6 seconds

Power On Reset

Rloader as Kernel or Bootloader?It's a trade-off between your boot time and management cost

MaintainenceOnce kernel/TOI changes, you need to re-implement

ComplexicityHow to restore pages?

Resume point? PC value?

Improved room might be limited

Further OptimizationRe-construct initcall stages

Try different algorithm out on compressing images

http://code.google.com/p/snappy/

Lazy loading

Put driver state into hibernation image

Summary

It's still far away from being a product

File system inconstencyPower failure as hibernation

Hardware solution is the sliver bullet?

The time of stepping into hibernation is also needed to concern

Demo

Resourcehttp://elinux.org/Boot_Time

http://tuxonice.net/

http://gitorious.org/improving-meego-boot-up-time/t2t/commit/d29d8576cf7969c1240e9f6420404c6329d3c524

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

27 May 2011Conference

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