_LINUXBOOT ppt

8/13/2019 _LINUXBOOT ppt

1/27

Reducing Boot Time:Reducing Boot Time:

Techniques for Fast BootingTechniques for Fast Booting

Chris Hallinan

Field Applications Engineer

Author: Embedded Linux Primer


2/27

Agenda

Introduction and Overview Hardware Discussion

Software Components

Overview of Boot Sequence Bootloader Issues

Linux Kernel Optimizations

Tools

pplications!"serland


3/27

Introduction

#ast Boot is Important to $an% &roducts Consumer' utomotive' $edical Devices' etc(

Si)nificant )ains w( minimal investment

#irst' define *+oot,( Does it mean-

Splas. screen/ 0st user process started/ Device full% up and runnin)' connected/

Boot time is affected +% man% factors- Hardware Desi)n Bootloader Implementation Kernel Confi)uration pplication &rofile


4/27

2008 MontaVista Software - Confidential 4

Typical Boot Sequence Optimization Opportunities

Bootloader $a% +e multiple sta)es

1emove support for unused features

$odif%!remove .ardware pro+in) features

Keep it Simple' Small -2

Kernel $an% opportunities for optimization

Low .an)in) fruit can +e eas% to 3pluc43

pplications $ost are up to %ou5

$ost initialization is serial

Ta4e measurements to decide w.ereto focus5

Power Applied

Pwr/Clk/Reset

Bootloader

Kernel Init

Root FS Mount

Userland Apps


5/27

Bootloader Considerations

Bootloader .as two primar%responsi+ilities-

Initialize C&"!Hardware 6minimall%2 Locate' load and execute a 4ernel ima)e

$a% involve several steps' includin) device I!O'decompression' etc(


6/27

Bootloader Considerations

$ost +ootloaders .ave man% more features

7sp( loo4 for an% t%pe of +us enumeration Lots of useful *development, functionalit% d.cp' tftp' pci scan' mem utils

device initialization' #las. utilities' etc

In a production s%stem' man% of t.ese features ma% +eunnecessar%

Disa+lin) t.ese features can .ave a si)nificant impact on+oot time

#or fast +oot' )et t.e +ootloader out of t.ewa% quic4l%

1emem+er' small 88 fast


7/27


Kernel Image Optimization

"se "ncompressed Kernel Decompression can ta4e several seconds5 Tradeoff- more #las. stora)e required

Kernel +uild produces two ima)es9 Ima)e and zIma)e 61$2 O+viousl%' zIma)e is t.e compressed

version

On i($:;0' t.is saved on avera)e ? mS

@$$A' dependin) on C&" speed' #LSHspeed(((

9Details var% for eac. arc.itecture' 1$ discussed .ere


8/27


Linux Kernel Configuration

7liminate "nnecessar% Kernel Options

1educes 4ernel size Speeds up 4ernel loadin) In some cases' will reduce 4ernel init time

once 4ernel is loaded

T%pical default 4ernel confi) contains lotsof 3stuff3 6i(e( features2 %ou ma% not need- $D!1aid support' I&v' umerous #ile

S%stems' 7xtended &artition support' etc( De+u) features suc. as 4ernel s%m+ols'

i4confi)' etc( $an% are compiled in features and increase

4ernel size


9/272008 MontaVista Software - Confidential 9

Kernel Config Options to Consider Disabling

CO#IE$D

1ID!LA$ support CO#IEID7

Saves init time ifnot used on HF w!

ID7 ctrlr Can also use

.dx8nopro+e

CO#IE&CC1D

CO#IEHOT&L" 1emove support for

.otplu) if notrequired

CO#IEIKCO#I 1emoves support for

confi) info' ma4es 4ernelsmaller

CO#IED7B"EK717L

CO#IEKLLS@$S

CO#IEB" "sed for de+u) G can +e

removed if desired



More Interesting Kernel Config Options

C.ec4 etwor4in) options

Lots of functionalit% G do %ou need it all/ ie( 4ernel autoconf' multicast' advanced router' etc(

1emove support for unnecessar% #S features Default confi)s often .ave muc. of t.is ena+led

CO#IEDOTI#@

CO#IEIOTI#@

CO#IE:#S

CO#IE"TO#SE#S 6utomounter2

etc

1emem+er- Smaller 4ernel 8 #aster load

If in doubt, make small changes. Test early andIf in doubt, make small changes. Test early and

often so you can rollback breakages easily!often so you can rollback breakages easily!



Calibration Routines

$an% .ardware platforms spendconsidera+le time in cali+ration routines *Calculatin) Bo)o$ips(((, llows precise dela%62 routines

Can ta4e si)nificant time "se 4ernel command line- loopsJperJiff%-

lp8xxxxx

7as% to use- most platforms will displa%correct value in 4ernel lo) 6and to console2on startup



Driver Configuration

Consider %our s%stem requirements- F.at functionalit% must +e availa+le

immediatel%/ F.at functionalit% can +e deferred/ F.at drivers are not needed/

$odules 6CO#IE98$2' if unused' areirrelevant Fon3t affect 4ernel startup time



Driver Configuration

Drivers can +e preJcompiled into 4ernel or

+uilt as modules for loadin) later "se staticall%Jlin4ed drivers for functions

t.at must +e immediatel% availa+le

"se Loada+le $odules for deferred

functionalit% Caveat- if %ou can avoid CO#IE$OD"L7S'

4ernel will +e smaller9' t.us faster to load(T.ere is pro+a+l% also a minor .it to readin)

t.e driver from t.e #S instead of it +ein) int.e 4ernel

*Assumes minimal system, few drivers.



File System Selection

Consider C1$#S for initial readJonl% #S Compact and fast o ournalin) entries to scan on initial mount

"se tmpfs for !tmp' possi+l% !var' ot.ers

$ount writa+le #S later' suc. as ##SM onO1 #las.

Consider %our tolerance to sudden power off ournalin) file s%stems can protect +ut at a

cost of increased startup times



XIP Execute in Place

&rocessor does not cop% Kernel ima)e to D1$ 7xecutes directl% from 6O12 #las.

dvanta)es 1educes D1$ requirements 6and t.us power2 7liminates timeJconsumin) cop% from #las.

Disadvanta)es Dependin) on .!w arc.itecture' could +e muc.

slower i(e( +urst!cac.e performance' etc(

Cost of #las. G 4ernel must +e storeduncompressed

@our $ilea)e $a% Aar%



Remove Support for printk()

T.e *Brute #orce, approac. J CO#IE&1ITK

Completel% eliminates calls to print462 dvanta)es

Saves si)nificant 4ernel size' and t.erefore load time 7liminates man% +oot messa)es J decreasin) +oot

time

Disadvanta)e o 4ernel status messa)e are availa+le5 $a4es 4ernel de+u))in) ver% difficult

t.orou).l% tested 4ernel s.ould wor4 well .ere lternativel%' use *quiet, command line parameter

suppresses print4 output durin) +oot' preservin) t.eprint4 infrastructure to +e used postJ+oot



Tools K#T- Kernel #unction Timin)

1equires KLLS@$S' mentioned a+ove &rovides function call tracin) and timin)

Entry Duration Local Pid Trace---------- ---------- ---------- ------- ----------------------------- 162 11523 0 0 paging_init 162 11523 0 0 | free_area_init_nodes 162 11523 12 0 | | free_area_init_node

162 11511 11511 0 | | | _etext+0x2f0 162 11511 0 0 __alloc_bootmem_node 162 11511 11511 0 ! __alloc_bootmem_core 11787 2307 2307 0 vfs_caches_init_early 11787 1531 69 0 vfs_caches_init_early 11787 686 0 0 [ alloc_large_system_hash 11787 686 0 0 [ [ __alloc_bootmem 11787 686 0 0 [ [ [ __alloc_bootmem_nopanic 11787 686 686 0 [ [ [ [ __alloc_bootmem_core

13318 776 776 0 [ inode_init_early 14094 1208 641 0 mem_init 14094 567 4 0 # free_all_bootmem 14094 563 563 0 # # free_all_bootmem_core 15607 3851 3851 0 schedule 15607 3848 3848 0 schedule 15630 1573099 1573099 1 kernel_init 15666 81152 81152 4 schedule 15666 81139 81139 4 schedule



Tools Linux Trace Tool4it



Tools

print4 timestamps 6CO#IE&1ITKETI$72 ppends time info to print462 output 7na+les measurement of lon) operations'

esp( at +oot time

[ 1.321054] md: linear personality registered for level -1

[ 1.326629] md: raid0 personality registered for level 0[ 1.331964] md: raid1 personality registered for level 1[ 1.342289] TCP cubic registered[ 1.345936] NET: Registered protocol family 1[ 1.350403] NET: Registered protocol family 17[ 1.355816] RPC: Registered udp transport module.[ 1.360571] RPC: Registered tcp transport module.[ 1.366034] drivers/rtc/hctosys.c: unable to open rtc device (rtc0)[ 2.880506] IP-Config: Complete:[ 2.883575] device=eth0, addr=192.168.1.201, mask=255.255.255.0, gw=255...[ 2.892227] host=8349itx, domain=, nis-domain=(none),[ 2.897798] bootserver=192.168.1.9, rootserver=192.168.1.9, rootpath=[ 2.906152] md: Autodetecting RAID arrays.



Tools

initcallEde+u) reat wa% to )et a coarse view of s%stem

init timin)

4 msecs: initcall c02c7da0 t linear_init5 msecs: initcall c02c6bbc t init_sd6 msecs: initcall c02c7d78 t mpc83xx_wdt_init7 msecs: initcall c02cc450 t init_sunrpc10 msecs: initcall c02c01a8 t slab_sysfs_init15 msecs: initcall c02c8d50 t genl_init24 msecs: initcall c02c55c4 t serial8250_init

30 msecs: initcall c02c6364 t gfar_init34 msecs: initcall c02c743c t physmap_init72 msecs: initcall c02c9c60 t inet_init127 msecs: initcall c02c4e4c t pty_init4597 msecs: initcall c02cabe0 t ip_auto_config



An example of boot time reduction

i($:;0 1eference +oard Initial confi)uration-

?-; power on to command prompt 1ed+oot +ootloader ta4es 0? seconds

#inal Confi)uration etwor4in)' static I& Bus%+ox userland $an% 4ernel optimizations M(= Seconds J Kernel start to s.ell prompt $inimal en)ineerin) investment



Applications/Userland

Startup scripts-

void &erl!&%t.on dependencies 6will reduce #Ssize as well2 One custom startup script instead of usin) S%sA

Init and !etc!init(d

Cac.es 6+i) impact if %ou .ave a +i)userland2- Li+rar% Cac.e setup ICO #ont

&relin4 li+raries

"se tools to profile execution strace and ltrace can +e useful .ere



Additional Ideas and Resources

&arallelize t.e init tas4s *+oot, ever%t.in) at once drivers and tas4s can do t.eir several

seconds of waitin) at t.e same time

&rovide user feed+ac4 earl% Splas. screens' etc )ive impression t.at unit is +ooted w.ile

initialization continues ets +ac4 to definin) w.at *+ooted,

means(((




Save a canned memor% and s%stem stateto nonJvolatile stora)e so t.at +ootin) can occur as fast as t.e

memor% ima)e can +e read from dis4

6.i+ernation2( 1equires si)nificant stora)e

Suspend!1esume G man% consumerdevices almost never cold +oot( e()( man% *Smart &.ones, onl% cold +oot if

%ou remove N replace +atter%




Oprofile G S%stemwide Stat( &rofilin) for Linux On one proect' t.is .elped ID #las. as a +ottlenec4 #ocused on acceleratin) #las. I!O reduced +oot time

.ttp-!!elinux(or)!BootETime

Tim Bird3s OLS M?? presentation $et.ods to Improve Bootup Time in Linux .ttp-!!4ernel(or)!doc!ols!M??!olsM??v0Jpa)esJ=PJQQ(pdf

ran van de Aen' Linux &lum+ers ConferenceBootin) Linux in > Seconds 6xQ!Des4top focused26Sept 0Q' M??Q2 .ttp-!!lwn(net!rticles!MPPQ;!

$eld 6next slide2



A Meld

discussion

on Linux

startup...


27/27

_LINUXBOOT ppt

Documents

Transcript of _LINUXBOOT ppt