Status of Embedded Linux

1
Status ofEmbedded Linux CELF Plenary

• Tim Bird
• Sony Corporation
• CE Linux Forum Architecture Group Chair

2
Outline

• Kernel Highlights
• CELF Technology Watch List
• Other news
• Status Resources
• CELF Information

3
Kernel Highlights

• 2.6.24 highlights
• Coming in 2.6.25
• Interesting patches on the horizon

4
2.6.24 Kernel highlights

• Kernel markers
• LTTng may be coming soon
• Security modules framework was removed
• PM Quality of Service (QOS)

5
Coming in 2.6.25

• Here are a few things that made the merge window
• Kpagemap
• Matt Mackall's patches for fine-grained memory
  instrumentation
• More on this later
• Latency measurement API
• Support for LatencyTop
• See http//lwn.net/Articles/266153
• Smack - simple mandatory access control
• Need to see if it can makes sense to use in
  embedded

6
Interesting patches

• Here are a few things that appear to be coming
• Latency trace system
• Compiler instrumentation of kernel functions (gcc
  -mcount)
• Support for multiple tracers
• Steven Rostedt's isolation and generalization of
  RT-preempts latency-trace system
• Mem_notify
• Allows processes to avoid the OOM killer by
  responding to events and shrinking memory usage
  voluntarily
• See http//lwn.net/Articles/266361/

7
Technology Watchlist Review
8
Technology Watch List

• CE Linux Forum maintains a list of technologies
  that we are "watching"
• Things we are interested in
• Kind of like the Kernel Weather Forecast, but
  with focus on embedded
• List is reported on and updated at CELF meetings
• New page is on elinux wiki
• http//elinux.org/Technology_Watch_List
• We are deprecating the CELF wiki page.
• Page is out-of-date today, due to web site crash

9
Watchlist review

• Linux-tiny
• Kpagemap
• SquashFS
• AXFS
• LogFS
• LTTng
• SystemTap
• KFT
• Kernel trace system

• Printk-times arch support
• App Armour
• Tomoyo Linux
• Powertop
• PM QOS
• Userspace IO
• Kernel HOWTO document translations
• Libdlna

10
Watchlist detail - Size

• Linux-tiny
• CELF contracting with free-electrons (Michael
  Opdenacker - current Linux-tiny maintainer)
• Some patches being mainlined by Thomas Petazzoni
• See http//elinux.org/Linux_Tiny_Patch_Details
• Kpagemap
• Made 2.6.25 merge window!!
• CELF funded this work!
• Bloatwatch 2.0
• Matt Mackall just released Bloatwatch 2.0
• Tool to show kernel size regression (and to
  investigate size problems)

11
Kpagemap

• Can show details about every allocated (and
  virtual) page on the system
• Introduces PSS and USS size metrics
• PSS Proportional Set Size
• USS Unique Set Size
• Resources
• ELC presentation
• http//selenic.com/repo/pagemap/raw-file/tip/memor
  y-profiling.html
• LWN.net article
• http//lwn.net/Articles/230975/
• Visualization tools
• http//selenic.com/repo/pagemap

12
Watchlist detail - File systems

• SquashFS
• AXFS
• LogFS
• UBIFS

13
SquashFS

• Compressed read-only file system, with smaller
  compression than CramFS
• Latest release is 3.3, released Feb 5, 2008
• Not mainlined.
• Last attempt was several years ago.
• Philip Lougher was planning to do it on 5th
  anniversary of project, but injured his hand
• Any assistance you can give to Philip is
  appreciated!!

14
AXFS

• Advanced XIP file system
• Can profile applications, and only use XIP on
  some blocks
• Allows for fine-grained control over how much
  flash vs. RAM is used for an application set
• Last mainline attempt was summer, 2007
• Jared said at ELC Europe (Nov, 2007) that he
  might try another mainline attempt soon.

15
LogFS

• New flash filesystem to solve scalability
  problems with JFFS2
• Author is Jörn Engel
• LogFS keeps filesystem meta-data on flash instead
  of in memory
• Does not need to read lots of meta-data on mount
• This reduces mount time (and system boot time)
• But, it has some outstanding problems
• See Jörn's presentation

16
LogFS - Status

• See Jörn's talk
• Not mainlined
• Work is progressing
• Since mid January LogFS does write-back caching
  of metadata, for a big performance boost
• CELF is paying for work on the filesystem

17
UBIFS - Status

• File system build on UBI (flash block) instead of
  block layer
• Recently submitted for mainline inclusion by
  Nokia
• http//lwn.net/Articles/276025
• http//www.linux-mtd.infradead.org/doc/ubifs_white
  paper.pdf

18
Watchlist detail - Tracing

• LTTng (and Markers)
• SystemTap
• Kernel Function Trace (KFT)
• Printk-time arch support

19
LTTng

• LTTng Status
• Markers infrastructure mainlined in 2.6.24
• Next to mainline is actual LTTng core

20
Markers

• Infrastructure in kernel for static
  instrumentation
• Kprobes are for dynamic instrumentation
• Goal is very low overhead when not in use
• One compare, using immediate value
• No memory access or cache/TLB usage issues
• There's a new system to replace immediate values
  in kernel code, while kernel is running!!

21
Other Tracers and instrumentation

• SystemTap
• Nice system, but compilation step was not
  cross-compile aware
• Lineo Solutions demonstrated support for
  cross-execution here!
• More work needed for other platforms (e.g.
  Kprobes for MIPS)
• Kernel Function Trace
• Recent releases were broken on ARM
• CELF hired new maintainer - Nicholas McGuire
• New maintainer reports successful trace on MX31
  processor
• Need to rationalize with System Trace
• Printk-times arch support
• Many platforms have bad timer resolution for
  printk times
• CELF have fixes they should mainline

22
Watchlist detail - Security

• Tomoyo Linux
• LSM framework removed from kernel in 2.6.24
• Has some impact on non-mainlined security systems
• App Armour
• LSM framework removed from kernel in 2.6.24
• AppArmour group was let go from Novell
• See http//www.news.com/8301-13580_3-9796140-39.ht
  ml
• Smack included in 2.6.25 kernel

23
Watchlist detail - Security

• Embedded SE Linux
• Much progress recently
• See talks by Nakamura and Kohei
• Requires filesytem with xattrs
• Embedded configuration in as little as 700K

24
Watchlist detail - power management

• Powertop
• Shows timers and power state durations
• Need support for CPUIdle, in order to show
  C-state (power state) activity for non-Intel
  processors
• PM QOS
• Merged in 2.6.24
• Wolfson voltage regulator stuff

25
Watchlist - RealTime

• RT-preempt
• Ktimers was mainlined in 2.6.21
• Still working on ports to various platforms
• Remaining large pieces to mainline
• Threaded interrupts
• Sleeping spinlocks
• Latency tracer
• Latency tracer is actively being pushed to
  mainline
• CELF has worked on publishing porting and test
  results, and documenting tuning and testing "best
  practices"

26
Watchlist detail - Miscellaneous

• Kernel HOWTO document translations
• Chinese, Korean and Japanese translations are
  mainlined
• Libdlna
• Supports all profiles except MPEG-4 and WMV

27
Watchlist update

• Need to recover status into watchlist page after
  elinux.org web site crash
• Should be done in a few weeks
• Goal is to provide continuously updated
  information on key projects

28
Additional Stuff

• Just a few items CELF members are working on
• Stuff not on official watch list
• Organized by technology area

29
Bootup Time

• Embedded bootchart
• Toshiba work - See Jamboree18

30
System Size

• SLUB vs. SLAB vs. SLOB
• Both SLUB and SLOB have recently received some
  updates.
• SLUB is now the default memory allocator for the
  kernel
• But people aren't entirely happy with it
• SLOB vs. SLAB size comparison
• On x86, 128M system
• SLOB yields 180K more runtime memory than SLAB
• On ARM 32M system
• SLOB yields 150K more runtime memory than SLAB
• Still a big desire to see SLOB results and usage
  experience

31
Licensing

• Noise over GPL 3.0 has died down
• Kernel will stay GPL 2.x for now
• glibc 2.6.1 Release note
• The 2.6 and 2.6.1 releases of the GNU C Library
  are licensed under the LGPL version 2.1, and GPL
  version 2.1 for the non-library programs
  included, or any later version. We expect that
  the next non-bug-fix release of the C Library
  will migrate to a newer LGPL version.
• See http//sourceware.org/ml/libc-announce/2007/ms
  g00001.html

32
Graphics

• CELF interested in GstOpenMAX
• OpenMax is a graphics framework API promoted by
  Khronos (with several large CE companies as
  members)
• GstOpenMax is an open source implementation of
  OpenMax on top of GTK

33
Middleware

• DLNA
• CELF hosted the first ever open source DLNA
  summit, in Linz Austria
• CELF has donated several DLNA specifications to
  open source projects
• New dlna-dev mailing list
• In process of obtaining sample hardware for
  various DLNA projects
• DLNA summit 2 planned for ELC-Europe 2008

34
Mobile Phone stack wars

• Android
• Demo'ed and presented here
• LIMO
• Feb 4 - announced their Linux platform
• See LIMO press release
• http//www.limofoundation.org/press-releases/limo-
  press-releases/limo-rolls-out-world-s-first-global
  ly-competitive-linux-based-software-platform-for-m
  obile-devices.html
• New ARM Ultra-Mobile PC initiative
• See http//www.linuxworld.com/news/2007/100407-mon
  tavista-arm-linux-umpc.html?nlhtos100507linuxaler
  t1

35
Status Resources

• LinuxDevices.com
• http//www.linuxdevices.com/
• LWN.net kernel pages
• http//lwn.net/Kernel/
• Articles sorted by topic
• http//lwn.net/Kernel/Index/
• Linux Weather Forecast
• http//www.linux-foundation.org/en/Linux_Weather_F
  orecast
• CELF Technology Watch List page
• http//elinux.org/Technology_Watch_List

36
Some CELF Information
37
CE Linux Forum
The CE Linux Forum (CELF) is focused on the
advancement of Linux as an open source
platform for consumer electronics devices.
38
CELF History

• June 23, 2003
• Founder Panasonic, Sony
• Initial board members
• Hitachi, Toshiba, Sharp, Philips, Samsung, NEC,
  IBM
• About 50 member companies, now

39
CELF Basic Structure
Board of Directors
Marketing Group
Architecture Group
Technical Workgroup
Technical Workgroup
40
Membership by Geography
41
Membership by Industry
42
Technical Work

• Technical Workgroups
• Contract work
• Conferences
• Technical output
• Special Projects
• Open Source Education

43
CELF Technical Working Groups
44
Workgroups

• Audio, Video, Graphics
• Boot Technologies
• Digital Television
• Memory Management
• Power Management
• Real Time
• Security
• System Size

45
Audio, Video, Graphics

• Mission Help develop and enhance standard AVG
  layers for different profiles
• TV, handheld, etc.
• Previous Projects
• Integration of DirectFB and UHAPI
• GNOME Mobile and Embedded launch
• DirectFB porting work

46
Boot Technologies

• Mission Reduce boot up time
• Recent Projects
• LogFS support
• Application pre-linking
• XIP

47
Digital Television Profile

• Mission Help identify problem areas for DTV
  products, and fill gaps
• Recent Projects
• DLNA open source project evaluation
• DLNA community developer support
• Sent DLNA specifications to community project
  leaders
• Hosting the DLNA summit (2) in Europe

48
Memory Management

• Mission Improve memory management systems of
  Linux, for embedded products
• Candidate Projects
• NUMA for small systems
• Compressed cache evaluation
• Asymmetric nodes, variable page sizes
• SLUB/SLOB scalability and node affinity work
• Support for power-management control of memory
  extents

49
Power Management

• Mission Help reduce power usage
• Previous Projects
• Contract work to produce and mainline Power
  Management framework elements
• Have hosted BOFs and a PM Summit
• PM Quality-of-service feature

50
Real Time

• Mission Enhance Real Time performance of Linux
• Recent Projects
• RT-preempt patch validation
• "Realtime testing best practices" document

51
Security

• Mission Enhance security for embedded devices
• Projects
• Hardware donation to Linux security project
• CELF member work
• Embedded SELinux work

52
System Size

• Mission Reduce memory utilization
• Projects
• System-wide memory profiling
• Linux-tiny revival
• Bloatwatch funding

53
Contract Work
54
Contractors

• Matt Mackall
• Matt Locke
• Bill Traynor
• Michael Opdenacker
• Nicholas McGuire
• Jörn Engel

55
Conferences
56
Conferences overview

• Embedded Linux Conference (ELC)
• Ottawa Linux Symposium (OLS)
• Regional Jamborees
• ELC-Europe
• Japan trade shows

57
Embedded Linux Conference

• Held April each year in San Jose, California
• Target audience is embedded Linux developers
• Is an open, community-oriented conference
• Not a trade show
• First conference with a focus on on embedded
  Linux
• This year is our fourth year

58
Ottawa Linux Symposium

• Each year, CELF is a sponsor of the symposium
• CELF members gave several presentations and BOFs
• Hand out prizes, do demos, etc.
• Goal is to interact with other (non-embedded
  developers) and show them our issues

59
Regional Jamborees

• Casual, one-day, one-track conferences held in
  regional areas
• Japan Regional Jamboree
• Held every other month
• Presentations and discussion in native language
• Content is translated to English, after the event
• Jamboree 20 wil be held next week
• These have great technical content
• See http//elinux.org/Events

60
ELC Europe

• Planned for November 6,7
• In Ede, The Netherlands
• Joint conference with NLUUG
• Call for sessions is already out
• Check your bag for a paper

61
Technical Output
62
Review of technical output

• Presentations and documents
• Patches
• Embedded Linux Wiki

63
Documents on Public wiki
64
Patches

• Goal is always to push patches upstream
• CELF doesn't submit patches itself (except via
  its contractors)
• Linux-tiny
• RTC no-sync patches
• kpagemap
• Encourage CELF members to submit directly to
  mainline projects
• LTTng, Kprobes and SystemTap
• RT-preempt work
• Power Management Quality-of-Service
• Board support

65
Special Projects
66
Special Projects

• Embedded Linux Wiki
• Hardware donations

67
Embedded Linux Wiki

• http//elinux.org/

68
what it looks like
69
What elinux.org Is (and is not)

• A new resource for the whole embedded Linux
  community
• Mostly technical documents and information,
  accumulated over years
• Not a CELF-only site
• Not just for CE companies or for CELF members.
• Not an encyclopedia
• elinux.org and Wikipedia are complimentary
• Not a news site

70
Site Status

• About 490 pages with real content
• 540 uploaded files
• 350 registered users
• 3400 page edits
• 285,000 page views
• Currently showing a backup of content from
  February

71
Content highlights

• Boot time reduction
• Memory reduction
• Processor docs
• CELF specifications
• power management,
• multimedia
• etc.
• Hardware hacking

• Real-time
• Toolchains
• Products running Linux
• Companies involved with Linux
• Vendors, Semi-conductor, CE Product companies
• Events

72
Hardware Donations

• Architecture Group donates hardware to community
  developers
• Example 1 Mobile phone to power management
  developer
• Example 2 Nokia tablet to security analysis tool
  author
• Working on a bunch of hardware for DLNA developers

73
Open Source education

• White papers, articles and talks about why and
  how to participate in the Linux community

74
Closing Remarks

• It was nice to see you all this year.
• Keep up the good work.

Linux is destined to dominate the embedded market!

• Let's have fun doing it!

75
Thanks

• Questions?

76
Questions and Answers