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[Rohan Garg <rohan16garg@xxxxxxxxx>]

I've worked around this issue in Kubuntu Utopic 14.04 with kubuntu-
settings 1:14.10ubuntu3 [1]

It would be awesome if someone from the foundations team could have a
look into why Ubuntu can't switch back to CFQ.

[1] https://launchpad.net/ubuntu/+source/kubuntu-settings/1:14.10ubuntu3

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https://bugs.launchpad.net/bugs/1310402

Title:
  Userland depends on ionice idle but default scheduler is "deadline".

Status in “linux” package in Ubuntu:
  Triaged

Bug description:
  Userland depends upon the idle feature of the CFQ scheduler, this can
  lead to extreme desktop sluggishness with the default deadline
  scheduler due to IO blocking.

  In my case, the KDE baloo indexer was indexing all of my files, and
  making other desktop processes block.  The baloo processes are set to
  idle IO priority to avoid this problem but this was not being honored.

  From the information I have found online and in the ionice man page,
  the idle priority only is useful with the CFQ scheduler.

  KDE Baloo indexer sets it's processes to use "idle" priority

  the man-db cronjobs also use idle priority
  root@sirius:/etc# grep idle cron.daily/man-db 
  iosched_idle=
      iosched_idle='--iosched idle'
          --oknodo --chuid man $iosched_idle -- -c \
                        $iosched_idle \

  The compiled in default scheduler is "deadline"
  root@sirius:/boot# grep DEFAULT_IOSCHED config-3.13.0-24-generic 
  CONFIG_DEFAULT_IOSCHED="deadline"

  from the ionice man page:
  Linux supports I/O scheduling priorities and classes since 2.6.13 with the CFQ I/O scheduler.

  root@sirius:/boot# uname -a
  Linux sirius 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-generic 3.13.0.24.28
  ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
  Uname: Linux 3.13.0-24-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC1:  zmc        2658 F.... pulseaudio
                        zmc        3010 F.... pulseaudio
   /dev/snd/controlC0:  zmc        2658 F.... pulseaudio
                        zmc        3010 F.... pulseaudio
  CurrentDesktop: KDE
  Date: Sun Apr 20 17:23:28 2014
  HibernationDevice: RESUME=UUID=dea47071-fda3-4725-a9c5-1f4fc531e6ef
  InstallationDate: Installed on 2014-04-18 (2 days ago)
  InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1)
  MachineType: Acer Aspire 7551
  ProcFB: 0 radeondrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-24-generic root=/dev/mapper/hostname-root ro quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-24-generic N/A
   linux-backports-modules-3.13.0-24-generic  N/A
   linux-firmware                             1.127
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 10/26/2010
  dmi.bios.vendor: Phoenix Technologies LTD
  dmi.bios.version: V1.15
  dmi.board.asset.tag: No Asset Tag
  dmi.board.name: Aspire 7551
  dmi.board.vendor: Acer
  dmi.board.version: V1.15
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: Acer
  dmi.chassis.version: V1.15
  dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvrV1.15:bd10/26/2010:svnAcer:pnAspire7551:pvrV1.15:rvnAcer:rnAspire7551:rvrV1.15:cvnAcer:ct10:cvrV1.15:
  dmi.product.name: Aspire 7551
  dmi.product.version: V1.15
  dmi.sys.vendor: Acer

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