Status of Embedded
Linux
Embedded Linux
Community News
December 2010
Tim Bird
CELF Architecture Group Chair
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Agenda
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Technology quick update
Embedded Linux Summit report
CE flag version
Yocto
Upcoming conferences
Miscellaneous news
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Technology status (quick
updates)
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Stable tracing APIs
TTY-based group scheduling
Checkpoint/restart for applications
Bootchart2
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Stable tracing APIs
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Goal is to designate certain tracepoints as
stable, and make them available long-term to
user space
Some people want stable API and others
don’t
Decided at Kernel Summit to do it, but then
negative feedback was received on kernel
mailing list
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TTY-based group scheduling
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Automatically places processes in control
groups, based on controlling TTY
Then implements “fairer” scheduling between
control groups
Prevents a kernel compile from interfering too
much with interactive tasks
Uses a scheduling mechanism that has been
in the kernel for a long time (control groups)
– Which, IMHO, demonstrates that there’s a lot of
technology in the kernel that is going unused in
embedded
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Checkpoint/Restart
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Ability to checkpoint and restart (like suspend
and resume) an application
System retains open files, memory maps,
signals, and other kernel-managed resources
Primary goals are robustness (recovery) and
runtime application migration
I want to use it to improve boot-up time (on a
per-application basis)
– I can’t help it, I instinctively look for boot time
improvements
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Bootchart 2
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Rewrite of most bootchart elements:
– Capture is in C instead of shell script
– Visualizer is in python instead of Java
– Lots of bugfixes and improvements to
visualization
• example: transparency for CPU utilization – in
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original bootchart this showed 0 utilization lots of
times when it was not appropriate
Looking at using trace events instead of
polling
– Should improve performance and accuracy
• (Note – would be nice to have stable tracepoints)
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Syslink
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Interprocessor communication mechanism
Would be really nice to have a standard
system in Linux for IPC between cores in
multi-core systems
TI willing to donate syslink, but it needs a lot
of modification to be accepted into mainline
– Much discussion at Plumbers about alternatives
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and possible solutions
Is something to watch
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Embedded Linux Summit
• Meeting of CE vendors, semi-conductor
vendors, Linux vendors, community leaders
• Held one in Japan – September 30, after
LinuxCon
• Held one in Cambridge, UK – October 26,
before ELCE
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Embedded Linux Summit
(cont.)
• Some key initiatives
– Legal wording for IP procurement, to promote
open source driver availability
– CE Flag Version – a longterm maintained version
of the Linux kernel
– Information base of IP blocks and corresponding
drivers
– Projects to decrease embedded Linux distro and
tools fragmentation
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IP procurement language
• Some companies saying that not enough
customers were asking for open source
drivers to justify cost of writing them
• CE and semi-conductor companies will try to
use language in their procurement contracts
which encourages suppliers to provide open
source drivers
– HP has done this successfully
– Language is not binding
– Supplier has to “opt out”, which means they have
received the message that open source drivers
are desirable
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CE Flag Version
• Problem:
– Embedded groups have lots of different kernel
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versions
– Some versions are supplied by semiconductor
vendors, and it is hard to change because porting
drivers would be required
– Would decrease integration cost to CE
companies if supply chain used fewer kernel
versions
Solution:
– Designate specific kernel version for a period of
time, and try to focus supply chain on that version
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Flag Version details
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Decided to promote kernel version 2.6.35
Strange confluence of many players at once:
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Andi Kleen is the maintainer of the branch
• See http://lkml.org/lkml/2010/12/3/35
To be called “longterm” (not “stable”)
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• Android, Linaro, Meego, Sony
– GregKH making some changes to how stable is
maintained
Longterm branches use same rules as stable
• See Documentation/stable_kernel_rules.txt
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Yocto project
• Intel /Linux Foundation publicly announced Yocto
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project at ELCE
Attempt to consolidate effort on a single build
system, and other development tools
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Chose Poky, which is an Open Embedded derivative
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TI, Palm/WebOS, Dell
MontaVista, Wind River, Mentor Graphics
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Some issues with governance and relationship with Open
Embedded
Look for LWN.net article soon
• OpenEmbedded seems to have critical mass
• Important Yocto meeting held
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Upcoming conferences
• Embedded Linux Conference 2011
– April 11-13 - in San Francisco
– CFP should go out soon
• Had to delay because of web site transition with
Linux Foundation
• LinuxCon Japan 2011
– June 1-3 - in Yokohama
• ELC Europe 2011
– October 26-28 - in Prague
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Consortia
• Linaro
– Released Linaro 10.11
– Have a nice roadmap of technical features they
want to accomplish
– Tool and Kernel highlights:
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Support for valgrind on ARM
Support for Neon instructions
Assist in mainlining Android patches
Are working to get ARM device trees mainlined
(shooting for 2.6.39)
• CELF and Linux Founding are merging
– Lots of legal details being taken care of
• Agreements from all contractors
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Miscellaneous News
• Mentor Graphics acquires CodeSourcery
• Sony ships Sony Internet TV
– First non-phone Android product endorsed by
Google
• Google ships Android Gingerbread SDK
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Status of CELF work
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Agenda (CELF work)
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CELF contract work
Open Project Proposal
Hardware donations
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Contract work completed this
year
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ARM enhancements for U-boot
Smemcap in busybox
Bootchart in busybox
Most of function-sections work mainlined
SquashFS LZO support (not a CELF
contract, but an LG kernel contribution)
Flash filesystem testing
– Was presented and discussed at ELCE
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Contract work of interest
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YAFFS mainline
Trace format standard
RT-preempt online training
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Mainline YAFFS2
• Description:
– YAFFS2 is a popular NAND flash filesystem
• Is used by Android
– Add support for YAFFS2 to mainline kernel
• Contractor: Aleph One Ltd
• Google is Co-Sponsoring this project
• Status:
– Several patch sets have been submitted to
mainline
– Were reviewed by IBM Linaro rep (Arnd
Bergman)
– Are still hoping for acceptance by end of the year.
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Trace format standard
• Description:
– Create a single trace format standard for the
embedded industry
• Contractor: Efficios (Matthieu Desnoyers)
• Status:
– Matthieu published several drafts of the Trace
Format document.
– It was reviewed by Steve Rostedt, and feedback
was provided
– Latest draft was reviewed and approved (Dec. 8)
by the Tool Infrastructure Work Group of the
MultiCore Association
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RT-preempt tutorial
• Description
– Create training and tutorial materials for using
RT-preempt patchset and feature
• On-line course to be put on eLinux wiki
– Free for public use
• Contrator: K Computing (Kevin Dankwardt)
• Status:
– Expect completion by December 31
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CELF Open Project Proposal
• You can suggest projects to fund for 2011
• Just opened proposal period on Tuesday
• For a submission, think about…
– What did you spend your time working on, on
Linux, in the last year?
– What would have saved you time and effort?
• Don’t have to be a member of CELF or the
Linux Foundation
• See http://elinux.org/CELF_Open_Project_Proposal_2011
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Contract work notes
• This year, because of merger, CELF has
double its regular contractor budget
• Some possible projects were discussed at
the Embedded Linux Summit, and at the
Kernel summit
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Candidate contract projects
• Add fastboot support to Linux
• Fast symbol resolution for module loading
• UBIL/UBI checkpointing – scalable UBI-attach
time
– Discussed with Thomax Gleixner at kernel summit
• Mainline RT-preempt patch set
• Link-time optimization (for size)
– Support for ‘whole-program’ compiler option
• Help with MIPI spec availability
• Kexec applet in busybox
• IP block driver database
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More Candidate projects
• Watchdog framework for the Linux kernel
– Repeat from last year
– This barely missed funding, but this year we have
more money!
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Binary analysis tool enhancements
Boot parameter caching
Continued Flash Filesystem testing
BTRFS on UBI
Sparse IRQs on ARM
Unified ARM version support (Linaro?)
Improved defconfig
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Hardware donations
• Donation for developer doing BKL removal
paid off
– We bought him a board, and he submitted
several patches with BKL lock removals
• Have approved donation for Android
developer
– Plan is to use bootchart2 and document results
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Thanks for your time
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