RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan...
Transcript of RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan...
![Page 2: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/2.jpg)
“Famous last words, but the actual patch volume _has_ to drop off one day. We have to finish this thing one day."
-- Andrew Morton September, 2005 (2.6.14)
![Page 3: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/3.jpg)
![Page 4: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/4.jpg)
2.6.27 -> 2.6.31++
(October 9, 2008 to September 18, 2009)
48,000 changesets merged 2,500 developers 400 employers
The kernel grew by 2.5 million lines
![Page 5: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/5.jpg)
2.6.27 -> 2.6.31++
(October 9, 2008 to September 18, 2009)
48,000 changesets merged 2,500 developers 400 employers
The kernel grew by 2.5 million lines
That come out to:140 changesets merged per day7267 lines of code added every day
![Page 6: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/6.jpg)
The employer stats
None 19%Red Hat 12%Intel 7%IBM 6%Novell 6%unknown 5%Oracle 4%consultants 3%Fujitsu 2%Renesas Tech 2%
Atheros 2%academics 2%Analog Devices 2%AMD 1%Nokia 1%Wolfson Micro 1%Vyatta 1%HP 1%Parallels 1%Sun 1%
![Page 7: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/7.jpg)
2.6.27 (October 9, 2008)
Ftrace
UBIFS
Multiqueue networking
gspca video driver set
Block layer integrity checking
![Page 8: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/8.jpg)
2.6.28 (December 24, 2008)
GEM graphics memory manager
ext4 is no longer experimental
-staging tree
Wireless USB
Container freezer
Tracepoints
![Page 9: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/9.jpg)
2.6.29 (March 23, 2009)
Kernel mode setting
FilesystemsBtrfsSquashfs
WIMAX support
4096 CPU support
![Page 10: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/10.jpg)
![Page 11: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/11.jpg)
![Page 12: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/12.jpg)
2.6.30 (June 9)
TOMOYO Linux
Integrity measurement
ext4 robustness fixes
R6xx/R7xx graphics support
Adaptive spinning mutexes
Object storage device support
FS-Cache
Nilfs
preadv()/pwritev()
Threaded interrupt handlers
![Page 13: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/13.jpg)
2.6.31 (September 9)
Performance counter support
Char devices in user space
Kmemleak
fsnotify infrastructure
TTM and Radeon KMS support
Storage topology
![Page 14: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/14.jpg)
...about finished?
![Page 15: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/15.jpg)
...about finished?
...so what's left?
![Page 16: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/16.jpg)
2.6.32 (early December)
Devtmpfs
Lots of block scalability work
Performance counter improvements
Scheduler tweaks
Kernel Shared Memory
HWPOISON
![Page 17: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/17.jpg)
Networking
“Based on all the measurements I'm aware of, Linux has the fastest & most complete stack of any OS.”
-- Van Jacobson
![Page 18: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/18.jpg)
But...
Scalability remains a problem
Especially with:High network speedsSmall packets
![Page 19: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/19.jpg)
Packet filtering and firewalling
iptables has served us well since 2.4
Problems:Much duplicated codeDifficult user-space interfaceInflexible
![Page 20: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/20.jpg)
Nftables
Remove protocol-awareness from the kernel...replace with a dumb virtual machine
Rules are translated in user space
AdvantagesMuch smaller code baseGreater flexibilityBetter performance
![Page 21: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/21.jpg)
Other networking stuff
Network namespace development...still...
Netfilter improvements
802.15.4 stack (Zigbee and more)2.6.31
Lots of wireless driver work
![Page 22: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/22.jpg)
Filesystems
![Page 23: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/23.jpg)
ext4
AdvantagesBetter performanceMany limits liftedext3 compatibility
Still stabilizingBut generally works quite well
![Page 24: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/24.jpg)
Btrfs
A totally new filesystem
AdvantagesPerformanceFull checksummingSnapshotsInternal volume management / RAID
Merged for 2.6.29Still very experimental
![Page 25: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/25.jpg)
Solid-state storage
Rotating storage is dying...well, maybe...
Solid-state devices are coolFastPower-efficientShock-resistant
![Page 26: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/26.jpg)
Solid-state storage
Also presents some challenges...
![Page 27: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/27.jpg)
![Page 28: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/28.jpg)
![Page 29: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/29.jpg)
![Page 30: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/30.jpg)
![Page 31: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/31.jpg)
![Page 32: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/32.jpg)
![Page 33: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/33.jpg)
![Page 34: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/34.jpg)
SSD: What to do?
Figuring out TRIM/DISCARD support
Using topology information
Smarter filesystemsbtrfs, nilfs, ubifs, ...
![Page 35: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/35.jpg)
Solid-state storage
The longer-term problem:SSDs will soon be capable of 100,000+ ops/secondWill the kernel be able to drive them that fast?
![Page 36: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/36.jpg)
Robustness guarantees
ext3 raised the bar for crash robustness
ext4 tried to lower it again
![Page 37: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/37.jpg)
Robustness guarantees
ext3 raised the bar for crash robustness
ext4 tried to lower it again
People complained.
![Page 38: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/38.jpg)
I want a pony!
![Page 39: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/39.jpg)
“No one ever, ever wrote "creat(); write(); close(); rename();" and hoped they would get an empty file if the system crashed during the next 5 minutes.”
-- Valerie Aurora
![Page 40: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/40.jpg)
What kind of guarantees do we owe our application developers?
![Page 41: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/41.jpg)
New APIs?
fbarrier()
acall()
readdirplus()
copyfile() [formerly reflink()]
kevents
A replacement for sockets
![Page 42: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/42.jpg)
“Over the years, we've done lots of nice 'extended functionality' stuff. Nobody ever uses them. The only thing that gets used is the standard stuff that everybody else does too.”
-- Linus Torvalds
![Page 43: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/43.jpg)
![Page 44: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/44.jpg)
Virtualization
Mostly done - in the kernel, at leastXen Dom0 still out-of-tree
Remaining work: performance, management
![Page 45: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/45.jpg)
KSM
Kernel shared memory
Scan memory for identical pagesDump duplicates and share one copyPages marked copy-on-write
Merged for 2.6.32
![Page 46: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/46.jpg)
Compcache
Swap out memory - to memorycompress it on the way
Can double the amount of apparent memory
![Page 47: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/47.jpg)
Containers
Lots of namespace work doneStill stabilizing
Yet to do:Resource controllersCheckpoint/restart
Photo: photohome_uk
![Page 48: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/48.jpg)
Hardware support
Near universal
A few remaining problemsGraphics adaptersSome network adapters
The -staging treeA home for substandard drivers
![Page 49: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/49.jpg)
Power management
A variation on the hardware support problem
![Page 50: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/50.jpg)
Power management
Photo: Terren in Virginia
![Page 51: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/51.jpg)
Power management
Coming soon: runtime power managementBetter control of devices in a running system
![Page 52: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/52.jpg)
Realtime
“While we never had doubts that it would be possible to turn Linux into a real time OS, it was clear from the very beginning that it would be a long way until the last bits and pieces got merged.”
-- Thomas Gleixner
![Page 53: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/53.jpg)
Status of realtime
Code is mostly stableShipped by numerous vendors
User-visible changes are all in mainline
What's not:Threaded interrupt handlersSleeping mutexesLots of bits and pieces
![Page 54: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/54.jpg)
Security
TOMOYO LinuxPathname-based mandatory access control2.6.30
Integrity measurement2.6.30
Still waiting:AppArmorfanotify
Open issue: sandboxing
![Page 55: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/55.jpg)
Tracing
Photo: Armel Genon
![Page 56: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/56.jpg)
SystemTap
A powerful dynamic tracing environment
Some problemsComplex, difficult to useRequires lots of ancillary dataDisconnect with kernel community
![Page 57: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/57.jpg)
Ftrace
Lightweight kernel tracing facilityPopular with kernel developers
Lots of static tracing optionsMaybe dynamic tracing in the future
Where a lot of the action is
![Page 58: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/58.jpg)
Perfcounter Perf Events
Access to performance monitoring registersUseful for low-level optimization
Integrated with tracepoints
Lots happening in this area
![Page 59: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/59.jpg)
LTTng
Linux Trace ToolkitWell-developed static tracing toolkitExtensive user-space tools
![Page 60: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/60.jpg)
Participation
The kernel development community is growing
We still have trouble with:Binary-only modulesWithheld codeLanguage barriersCultural differences...
Documentation/development-process
![Page 61: RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn · The Kernel Report RTLWS 11 edition Jonathan Corbet LWN.net corbet@lwn.net](https://reader036.fdocuments.net/reader036/viewer/2022081606/5dd10da2d6be591ccb63fe08/html5/thumbnails/61.jpg)
Questions?