![Page 2: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/2.jpg)
What we'll talk about
1) Process - releases and such (how we got to where we are)
2) Features and futures (Cool stuff and what it's good for)
![Page 3: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/3.jpg)
Cadence
The 2.6.34 cycle began February 25, 2010
Since then:Four releases have been made (another almost ready)49,079 changesets have been merged ...from 2,826 developers, 326 employers1.3 million lines of code have been added
![Page 4: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/4.jpg)
The process is working smoothly
![Page 5: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/5.jpg)
Who supports this work
Volunteers 17.6%Red Hat 11.7%unknown 7.7%Intel 6.7%Novell 4.8%IBM 3.7%Nokia 2.3%Consultants 2.2%Texas Inst. 2.2%Oracle 1.7%AMD 1.6%
Samsung 1.5%academics 1.4%Fujitsu 1.4%Renesas Tech. 1.4%Pengutronix 1.3%Google 1.2%Broadcom 1.1%Atheros 1.1%Analog Devices 1.1%Wolfson Micro 1.0%New Dream Net 1.0%
![Page 6: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/6.jpg)
The 2.6.21 version
Unknown 27%Red Hat 14%IBM 8%Novell 7%Linux Found. 5%Hobbyists 5%Intel 4%Oracle 2%Google 2%
SGI 2%MIPS Tech. 1%HP 1%Consultants 1%Nokia 1%Astaro 1%MontaVista 1%Linux Networx 1%Qlogic 1%
![Page 7: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/7.jpg)
![Page 8: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/8.jpg)
Who supports this work
Volunteers 17.6%Red Hat 11.7%unknown 7.7%Intel 6.7%Novell 4.8%IBM 3.7%Nokia 2.3%Consultants 2.2%Texas Inst. 2.2%Oracle 1.7%AMD 1.6%
Samsung 1.5%academics 1.4%Fujitsu 1.4%Renesas Tech. 1.4%Pengutronix 1.3%Google 1.2%Broadcom 1.1%Atheros 1.1%Analog Devices 1.1%Wolfson Micro 1.0%New Dream Net 1.0%
![Page 9: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/9.jpg)
2.6.34
May 15, 2010 (9,443 changes, 1,151 developers)
Asynchronous suspend/resumeperf lock, perf Python scripting supportLogFSCeph distributed filesystem
![Page 10: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/10.jpg)
2.6.35
Aug. 1, 2010 (9,801 changes, 1,188 developers)
perf kvmReceive packet/flow steeringMemory compactionIdle pattern detectionRAMoopsBtrfs direct I/O support
![Page 11: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/11.jpg)
2.6.36
Oct. 20, 2010 (9,501 changes, 1,176 developers)
AppArmor security moduleWakeup countsLIRC infrared driversNew OOM killerfanotifyConcurrency-managed workqueues
![Page 12: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/12.jpg)
2.6.37
Jan 4, 2011 (11,446 changes, 1,276 developers)
VFS scalability work (inode_lock removal)GFS2 is no longer “experimental”Block I/O bandwidth controllerPPTP supportBasic pNFS supportHugepage migrationWakeup sourcesBlock layer barrier work
![Page 13: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/13.jpg)
2.6.38
Mar. ??, 2011 (8,888 changes, 1,111 developers) (so far)
Per-session group schedulingDcache scalability workTransmit packet steeringBatch discardTransparent hugepagesMultitouch panel supportSCSI target subsystemBtrfs: read-only snapshots and LZO compression
You are here
![Page 14: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/14.jpg)
Stable updates
Mainline release is not the end of the story
Stable/longterm updates for:Serious bug fixesSimple hardware support (PCI IDs)Occasional backports
![Page 15: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/15.jpg)
Currently-maintained stable kernels
2.6.27Long term, deep freeze mode
2.6.32Base of a number of “enterprise” distributions
2.6.35Embedded “flag version”
2.6.362.6.37
Recent mainline releases
![Page 16: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/16.jpg)
Currently-maintained stable kernels
2.6.27Long term, deep freeze mode
2.6.32Base of a number of “enterprise” distributions
2.6.35Embedded “flag version”
2.6.362.6.37
Recent mainline releases
![Page 17: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/17.jpg)
Currently-maintained stable kernels
2.6.27Long term, deep freeze mode
2.6.32Base of a number of “enterprise” distributions
2.6.35Embedded “flag version”
2.6.362.6.37
Recent mainline releases
![Page 18: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/18.jpg)
What's coming?
![Page 19: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/19.jpg)
2.6.39
(Merge window is still open)
O_PATH opensOpen by file handleCLOCK_BOOTTIME...
![Page 20: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/20.jpg)
A new version numbering scheme?
No.
![Page 21: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/21.jpg)
A new version numbering scheme?
No.
(At least, not until we hit 2.6.42)
![Page 22: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/22.jpg)
Hardware support and vendor participation
![Page 23: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/23.jpg)
Good news: Broadcom releases an open driver
Qualcomm joins the Linux Foundation
Ralink starts submitting patches
Embedded flag kernel
![Page 24: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/24.jpg)
On the other hand:
Embedded graphics remains a problem
GPL compliance is spotty
![Page 25: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/25.jpg)
Power management
CPU power management works very well
Now working on memory,peripherals
![Page 26: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/26.jpg)
Power management
Android code still not merged.
We do have an alternative:Wakeup sources (2.6.36)Wakeup counters (2.6.37)Currently unused
![Page 27: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/27.jpg)
Power domains
Server or desktop PM is relatively simple
Newer systems less so
![Page 28: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/28.jpg)
![Page 29: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/29.jpg)
Dealing with complexity
Power domainsMap power relationships on each systemUsed to make power management decisions2.6.39 (maybe)
Media controller subsystemHandle connections between media processors2.6.39 (probably)
![Page 30: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/30.jpg)
Other things to watch for
ARM PAE support>4GB in your pocket2.6.39 maybe
Device tree support...over time
Vast numbers of new drivers...as always
![Page 31: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/31.jpg)
Solid-state devices
![Page 32: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/32.jpg)
Solid-state devices
![Page 33: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/33.jpg)
SSD challenges
Optimizing I/O patternsTransfer sizes and alignment
Block I/O subsystem scalability100 I/O operations/second -> 100,000+ IOPS
Communication with the deviceTRIM/DISCARD operations
![Page 34: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/34.jpg)
What will we do with that much fast memory?
![Page 35: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/35.jpg)
SCSI targets
Linux as a SCSI device
Useful for storage arrays and such
Replaces STGT
Two choices:LIO (now in-tree)SCST (out-of-tree)
![Page 36: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/36.jpg)
Dentry scalability
A directory entry (dentry) represents a name in the filesystem.
![Page 37: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/37.jpg)
The dentry scalability patches
Remove dcache_lockUse RCU for walking the dentry tree
Result: lockless file name lookup
![Page 38: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/38.jpg)
Filesystems
Ext4 Ready for production use
Ongoing scalability work
Occasional bug fixes
Ext2/ext3 code removal?
![Page 39: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/39.jpg)
Filesystems
Btrfs Almost there
Needs a filesystem checker
Remaining featuresDeduplicationRAID 4/5 support
Beginning deploymentDefault MeeGo filesystemDefault for Fedora 16?
![Page 40: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/40.jpg)
Filesystems
Others yaffs2Fast embedded filesystem2.6.39?
xfsContinued evolution
GFS2 no longer experimentalMerge with OCFS2?
![Page 41: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/41.jpg)
Transparent huge pages
Linux uses 4096-byte pages (most arch's)
![Page 42: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/42.jpg)
Transparent huge pages
The processor can deal with larger sizes
2MB is common
![Page 43: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/43.jpg)
Virtual address translations
Address translation is complicated
![Page 44: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/44.jpg)
The translation lookaside buffer
Caches address mappings-> Avoids that whole lookup process
The TLB tends to be smallOn this laptop: 128 instruction, 256 data
One 2M huge page saves 511 TLB entries!(If all internal pages are used)
Thus: huge pages make the system go faster
![Page 45: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/45.jpg)
Transparent huge pages
Linux has had hugetlbfs for yearsFiddly, administration-heavy mechanism
THP makes huge pages “just happen”Not as fast as hugetlbfsBut it works for everybodyMerged for 2.6.38
![Page 46: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/46.jpg)
Other memory management issues
WritebackOne of our biggest performance problems
Hybrid memory techniquesKSMTranscendent memory...
![Page 47: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/47.jpg)
Control groups
A means for grouping related processes
![Page 48: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/48.jpg)
Control groups
Are hierarchicalGroups can contain other groups
Are inheritedChildren stay in their parent's group
Are associated with controllersApply some policy to contained processes
![Page 49: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/49.jpg)
Control groups
Are hierarchicalGroups can contain other groups
Are inheritedChildren stay in their parent's group
Are associated with controllersApply some policy to contained processes
Are old news...merged in 2.6.24
![Page 50: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/50.jpg)
Group CPU scheduling
![Page 51: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/51.jpg)
Per-session group scheduling
Group scheduling is old...but nobody was using it
Per-session group schedulingMakes it all “just work”Interactivity improvements result2.6.38
![Page 52: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/52.jpg)
![Page 53: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/53.jpg)
![Page 54: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/54.jpg)
![Page 55: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/55.jpg)
Other control group stuff
Expanded group schedulingSystemd/gnome-session integrationNice separation of tasksBandwidth control
Memory controllerMore focused reclaim
Block I/O controllerHierarchical group I/O schedulingAsynchronous I/O control
...
![Page 56: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/56.jpg)
Deadline scheduling
Of interest to real time, media communities
Chilly reception at the 2010 kernel summitNeeds better use cases
Work continuesWe'll have it someday
![Page 57: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/57.jpg)
Realtime Preemption patch set
We'll have that someday too!
![Page 58: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/58.jpg)
Networking
Expand initial congestion window
2.6.39
DFS compliance2.6.40+
Ongoing issues:IPv6BufferbloatScalability Photo: Arenamontanus
![Page 59: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/59.jpg)
Security
Stackable modules2.6.40+
HardeningAn area of increased focus
User namespacesUnprivileged container creation
Photo: CarbonNYC
![Page 60: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/60.jpg)
Tracing and visibility
Continued ftrace and perf workEmphasis on usability and unificationAddition of tracepoints
Improved user-space tracing/debuggingSomeday
Still outside:SystemTapLTTng
![Page 61: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/61.jpg)
Things not discussed
Thousands of bug fixesVirtualizationAdditional architecturesDocumentationRAS improvementsCPU isolationInterrupt layer reworkClock enhancementsMM preemptabilityRegression trackingBKL removal...
![Page 62: Jonathan Corbet LWN.net corbet@lwnlwn.net/images/pdf/google-class/01-kreport.pdf · MontaVista 1% Linux Networx 1% Qlogic 1%. ... Embedded “flag version ... Of interest to real](https://reader031.vdocuments.us/reader031/viewer/2022022608/5b89e5617f8b9a770a8e8dba/html5/thumbnails/62.jpg)
Questions?