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[Launchpad Bug Tracker <661411@xxxxxxxxxxxxxxxxxx>]

[Expired for linux (Ubuntu) because there has been no activity for 60
days.]

** Changed in: linux (Ubuntu)
       Status: Incomplete => Expired

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https://bugs.launchpad.net/bugs/661411

Title:
  Multi-core load balancing not working properly after suspend to disk

Status in “linux” package in Ubuntu:
  Expired

Bug description:
  CPU: Intel(R) Core(TM) i7 CPU         860, 4 cores, hyperthreading

  Symptoms: After suspending to disk load balancing of processes across
  CPU cores is not working properly. Runnable processes have to share a
  CPU core even if idle CPU cores are available. This is particularly
  noticeable when running parallel builds (e.g. make -j8 ...). They take
  much longer and the GNOME system monitor applet shows that most CPU
  cores are idle when there is enough work to keep them all busy.

  A simple test to visualize the problem is to run "(while true; do
  true; done) & (while true; do true; done)" in bash and look at the CPU
  usage in top. After a fresh boot, the two subshells run with 100% CPU
  usage each, so each gets its own core to run on. When running this
  experiment after a suspend/resume cycle the two subshells run with 50%
  CPU usage each, so they're made to share a CPU core, although idle CPU
  cores are available.

  Steps to reproduce:
  * Boot system
  * log in as normal user
  * run the following command in a terminal window running bash: (while true; do true; done) & (while true; do true; done)
  * In a second terminal window run top and observe two bash processes at the top, each running with 100% CPU usage
    (each bash gets its own CPU core)
  * kill the two bash subshell processes
  * suspend to disk
  * wake up the system
  * Run the same command as above: (while true; do true; done) & (while true; do true; done)
  * In top the two bash processes run with 50% CPU usage
    (the two bash processes apparently share one CPU core, although idle cores are available)

  Expected result: load balancing should continue working after
  resuming. The two bash subshells should each run with 100% CPU usage.

  Actual result: load balancing is broken after resume. The two bash
  subshells have to share a CPU core even when idle CPU cores are
  available to balance the load.

  ProblemType: Bug
  DistroRelease: Ubuntu 10.10
  Package: linux-image-2.6.35-22-generic 2.6.35-22.34
  Regression: Yes
  Reproducible: Yes
  ProcVersionSignature: Ubuntu 2.6.35-22.34-generic 2.6.35.4
  Uname: Linux 2.6.35-22-generic x86_64
  NonfreeKernelModules: fglrx
  AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
  Architecture: amd64
  ArecordDevices:
   **** List of CAPTURE Hardware Devices ****
   card 0: Intel [HDA Intel], device 0: VT1828S Analog [VT1828S Analog]
     Subdevices: 2/2
     Subdevice #0: subdevice #0
     Subdevice #1: subdevice #1
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  fkuehlin   1753 F.... pulseaudio
   /dev/snd/pcmC0D0p:   fkuehlin   1753 F...m pulseaudio
  CRDA: Error: [Errno 2] No such file or directory
  Card0.Amixer.info:
   Card hw:0 'Intel'/'HDA Intel at 0xfbaf8000 irq 52'
     Mixer name	: 'VIA VT1828S'
     Components	: 'HDA:11064441,104383d0,00100100'
     Controls      : 35
     Simple ctrls  : 20
  Card1.Amixer.info:
   Card hw:1 'Generic'/'HD-Audio Generic at 0xfbbfc000 irq 53'
     Mixer name	: 'ATI R6xx HDMI'
     Components	: 'HDA:1002aa01,00aa0100,00100200'
     Controls      : 4
     Simple ctrls  : 1
  Card1.Amixer.values:
   Simple mixer control 'IEC958',0
     Capabilities: pswitch pswitch-joined penum
     Playback channels: Mono
     Mono: Playback [on]
  Date: Fri Oct 15 14:56:46 2010
  HibernationDevice: RESUME=UUID=8f6cfcae-9123-48f0-a9c6-1e962e6b726e
  InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100429)
  IwConfig:
   lo        no wireless extensions.
   
   eth0      no wireless extensions.
  MachineType: System manufacturer System Product Name
  ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.35-22-generic root=UUID=c9f4b289-89ae-42c0-ba57-13b1b26131da ro quiet splash
  ProcEnviron:
   PATH=(custom, user)
   LANG=en_CA.UTF-8
   SHELL=/bin/bash
  RelatedPackageVersions: linux-firmware 1.38
  RfKill:
   
  SourcePackage: linux
  WifiSyslog:
   Oct 15 14:55:59 Harpoon kernel: [17206.856773] ACPI Warning: Incorrect checksum in table [OEMB] - 0x03, should be 0xED (20100428/tbutils-314)
   Oct 15 14:55:59 Harpoon kernel: [17206.856958] ACPI Warning: Incorrect checksum in table [OEMB] - 0x03, should be 0xED (20100428/tbutils-314)
  dmi.bios.date: 03/25/2010
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 1408
  dmi.board.asset.tag: To Be Filled By O.E.M.
  dmi.board.name: P7P55D
  dmi.board.vendor: ASUSTeK Computer INC.
  dmi.board.version: Rev 1.xx
  dmi.chassis.asset.tag: Asset-1234567890
  dmi.chassis.type: 3
  dmi.chassis.vendor: Chassis Manufacture
  dmi.chassis.version: Chassis Version
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1408:bd03/25/2010:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnP7P55D:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion:
  dmi.product.name: System Product Name
  dmi.product.version: System Version
  dmi.sys.vendor: System manufacturer

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