April 22, 2023 CE Linux Forum Members Confidential

1

Embedded Linux BOF

Tim BirdSoftware Engineer, Sony ElectronicsChair, CE Linux Forum Architecture

Group

April 22, 2023 CE Linux Forum Members Confidential

2

Embedded Linux Stuff• Year in Review

• Shameless plug

• Embedded Linux wiki

• Lightning talks

April 22, 2023 CE Linux Forum Members Confidential

3

Year in Review

• Real-time

• Size

• Bootup Time

• Audio/Video/Graphics

• Security

• Power Management

• Mobile Phone

• Processor support

• Tools

April 22, 2023 CE Linux Forum Members Confidential

4

Realtime

• hrtimers (2.6.18?)

– clock sources (2.6.18)– HR timer API

• http://lwn.net/Articles/167315/

– ktimers explanation:• http://lwn.net/Articles/152436/

• Generic IRQ (2.6.18)

• Tickless Idle coming

April 22, 2023 CE Linux Forum Members Confidential

5

Rt-Preempt

• Mainline status– Most stuff in, “only” need:

• sleeping spinlocks

• threaded IRQs

• Priority Inheritance (2.6.18)– http://lwn.net/Articles/177838/

• Latency tracer

April 22, 2023 CE Linux Forum Members Confidential

6

Size

• Linux-tiny

• Squashfs

• Inode Slimming

• Unit-at-a-time compilation• Size Testing

– Bloatwatch

– Config size testing

April 22, 2023 CE Linux Forum Members Confidential

7

Linx-tiny mainlining

• small-8023.patch• fs_open-inlines.patch• inode-inlines.patch• fslocks-inline.patch• bloat-o-meter.patch• no-doublefault.patch• no-elf-core.patch• slob.patch• remove-vm86.patch• uid16.patch

April 22, 2023 CE Linux Forum Members Confidential

8

Inode Slimming Patches• brand new

– july 3 - Ted Tso (not mainlined yet)

• Tips:– Ted Tso - if you want to save memory taken up

by in-core inodes, the first thing you should do is disable the debugging options; they are responsible for a huge amount of bloat in the VFS inode structure

April 22, 2023 CE Linux Forum Members Confidential

9

Unit-at-a-time Compilation• Ingo Molnar patch to utilize gcc 4 unit-at-a-

time compilation– http://lkml.org/lkml/2005/12/28/68– http://lwn.net/Articles/165354/

• inline reduction– New _always_inline_ attribute:

• http://lwn.net/Articles/167315/

• http://lwn.net/Articles/165354/

April 22, 2023 CE Linux Forum Members Confidential

10

Size Testing• Bloatwatch

– http://testlab.celinuxforum.org/...

• Config size testing– Presentation at CELF Project BOF

April 22, 2023 CE Linux Forum Members Confidential

11

Security• AppArmour

– Lighter than SELinux– Good enough for embedded work??

• LSM in peril…

April 22, 2023 CE Linux Forum Members Confidential

12

Bootup Time• XIP - Execute in Place

– Old info: http://lwn.net/Articles/135472/– XAFS - new file system specifically for XIP

• Jared Hulbert (Intel) posted for comments:– http://lwn.net/Articles/182337/

April 22, 2023 CE Linux Forum Members Confidential

13

Power Management

• User-space software suspend• Latest kerfluffle over suspend phases

– Linus has posted a new patch, showing his method.

– See lwn.net: http://lwn.net/Articles/189467

• Linux PM summit– http://lwn.net/Articles/181687

– Main issues: See PM BOF 19:00 Room A

April 22, 2023 CE Linux Forum Members Confidential

14

Audio/Video/Graphics

• Big direct rendering update

– http://lwn.net/Articles/167315/

• New CELF AVG Spec. (2.0)– DirectFB, ALSA, OpenGL/ES, UHAPI

April 22, 2023 CE Linux Forum Members Confidential

15

Mobile phone stuff

• CELF specification still in-progress

• More organizations than you can “shake a stick at”:– CELF MPPWG– OSDL MLI– LIPS– “the new one”

April 22, 2023 CE Linux Forum Members Confidential

16

Tools• Tracing

– LTTgn just recently re-added lots of architecture support

– LTTng, KFT, LKST - See Tracing BOF, 19:00 Room D

• Memory Leak Tracker

• Compilers– Thumb support

April 22, 2023 CE Linux Forum Members Confidential

17

Other• Function re-ordering

– http://lwn.net/Articles/173657/

• GPL3– “Nothing to see here, move along…

April 22, 2023 CE Linux Forum Members Confidential

18

News from the Kernel Summit• LSM stays for now

• suspend/resume still messed up

• no transparent super-pages

• Kernel leaders sympathetic to size issue

• other stuff??

April 22, 2023 CE Linux Forum Members Confidential

19

Shameless plug• CELF Project BOF

– Friday night, 7:00 pm, Les Suites– CELF Test Lab demo– Config size testing– CABI CPU resource reservation– Japan Jamboree update– Technical showcase

April 22, 2023 CE Linux Forum Members Confidential

20

Embedded Linux Wiki• Place to store info on embedded Linux

• Starter material from CELF wiki

• Paid maintenance, to avoid wiki rot– CELF may fund, if plan looks good and there’s

community interest

• BOF this week to discuss

April 22, 2023 CE Linux Forum Members Confidential

21

Lightning talks• 2 minutes (max)

– what are you doing? / what is the issue? when will you publish!?

– make it quick and to-the-point– where to go for more info…

April 22, 2023 CE Linux Forum Members Confidential

22

Lightning topics