Consider disabling NEW_FAIR_SLEEPERS

Bug #436342 reported by Johan Kiviniemi
34
This bug affects 4 people
Affects Status Importance Assigned to Milestone
linux (Ubuntu)
Medium
Tim Gardner
Karmic
Medium
Tim Gardner

Bug Description

Due to latency problems with desktop interactivity when the NEW_FAIR_SLEEPERS scheduler feature is active, it was disabled by default for Linux 2.6.32, pending the bug being found and fixed.

http://git.kernel.org/?p=linux/kernel/git/x86/linux-2.6-tip.git;a=commitdiff;h=3f2aa307c4d26b4ed6509d0a79e8254c9e07e921

Please consider disabling it in Ubuntu kernels as well.

ProblemType: Bug
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ion 16762 F.... pulseaudio
CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
Card0.Amixer.info:
 Card hw:0 'SB'/'HDA ATI SB at 0xd2400000 irq 16'
   Mixer name : 'Realtek ALC268'
   Components : 'HDA:10ec0268,103c30f1,00100003 HDA:10573055,103c30f1,00100700'
   Controls : 15
   Simple ctrls : 12
Date: Fri Sep 25 05:39:59 2009
DistroRelease: Ubuntu 9.10
MachineType: Hewlett-Packard HP Pavilion tx2500 Notebook PC
NonfreeKernelModules: fglrx
Package: linux-image-2.6.31-10-generic-pae 2.6.31-10.35
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.31-10-generic-pae root=UUID=cb73d396-bca3-4c05-95a2-212a4cecc0b2 ro quiet splash
ProcVersionSignature: Ubuntu 2.6.31-10.35-generic-pae
RelatedPackageVersions:
 linux-backports-modules-2.6.31-10-generic-pae 2.6.31-10.12
 linux-firmware 1.19
RfKill:

SourcePackage: linux
Uname: Linux 2.6.31-10-generic-pae i686
WpaSupplicantLog:

dmi.bios.date: 02/17/2009
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: F.0B
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: 30F1
dmi.board.vendor: Quanta
dmi.board.version: 97.20
dmi.chassis.type: 10
dmi.chassis.vendor: Quanta
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnHewlett-Packard:bvrF.0B:bd02/17/2009:svnHewlett-Packard:pnHPPaviliontx2500NotebookPC:pvrRev1:rvnQuanta:rn30F1:rvr97.20:cvnQuanta:ct10:cvrN/A:
dmi.product.name: HP Pavilion tx2500 Notebook PC
dmi.product.version: Rev 1
dmi.sys.vendor: Hewlett-Packard

Revision history for this message
Johan Kiviniemi (ion) wrote :
Changed in linux (Ubuntu):
importance: Undecided → Medium
status: New → Triaged
Revision history for this message
Tim Gardner (timg-tpi) wrote :
Changed in linux (Ubuntu):
assignee: nobody → Tim Gardner (timg-tpi)
status: Triaged → Fix Committed
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package linux - 2.6.31-11.38

---------------
linux (2.6.31-11.38) karmic; urgency=low

  [ Stefan Bader ]

  * [Upstream] acerhdf: Limit modalias matching to supported boards
    - LP: #435958

  [ Tim Gardner ]

  * [Config] Added sata_via to d-i/modules/sata-modules
    - LP: #434827
  * SAUCE: (drop after 2.6.31) Disable iwl-1000 series wireless adapters
    - LP: #439285
  * [Upstream] i915: Fix i2c init message
    - LP: #409361
  * [Config] Add sym53c8xx.ko to virtual sub-flavour
    - LP: #439415

  [ Upstream Kernel Changes ]

  * sched: Disable NEW_FAIR_SLEEPERS for now
    - LP: #436342

  * ACPI video: ignore buggy _BQC
  * ACPI video: work-around BIOS AML bug in _BQC
    - LP: #428910
  * ALSA: hda - Added quirk to enable sound on Toshiba NB200
    - LP: #438318

 -- Tim Gardner <email address hidden> Thu, 01 Oct 2009 13:52:09 -0600

Changed in linux (Ubuntu Karmic):
status: Fix Committed → Fix Released
Revision history for this message
Markus Thielmann (thielmann) wrote :

Please notice that disabling NEW_FAIR_SLEEPERS made my system much slower. In fact, Karmic was the first release which allowed me to play tremulous in fullscreen with a nice speed. With NO_NEW_FAIR_SLEEPERS, the system is much slower.

Revision history for this message
Peter Cordes (peter-cordes) wrote :

Markus, and anyone else wondering about interactive performance regressions, NEW_FAIR_SLEEPERS is modifiable at run time; just run

echo NEW_FAIR_SLEEPERS | sudo tee /sys/kernel/debug/sched_features

grep --color=tty NEW_FAIR_SLEEPERS /sys/kernel/debug/sched_features

(Ubuntu mounts linux's debugfs at /sys/kernel/debug, not at /debug like you see referenced on the lkml threads talking about this.)

 To enable for every reboot, put
echo NEW_FAIR_SLEEPERS > /sys/kernel/debug/sched_features
 in /etc/rc.local, or whatever.

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