Public bug reported:
It appears that there is an issue with the Completely Fair Scheduler (CFS) not
intereacting well with sleep commands. I have written up a test program to help
demonstrate the issue and it can be found at:
www.github.com/daveisfera/test_sleep/
The test outputs wall time (CPU clock), user time, and system time, but usually
only the wall time and user time outputs are meaningful because the system time
is so small and usually within the standard deviation for all tests.
I have also attached the results from running this test on an HP
Pavilion dm4 and I believe that the gap at the low number of threads is
caused by either the processor going into a power saving state because
of the sleeping and/or a poor interaction with HyperThreading
(scheduling the 2 threads on logical cores rather than separate physical
cores).
Because of this, I then ran 4 instances of:
schedtool -a <CPU#> -e nice -19 yes > /dev/null
so that all of the cores would be kept busy during the sleeping and this had an
unexpected effect of causing the wall time to increase significantly. I am not
sure what the cause of the wall time increase is, but it does help the user
time plot display the gap between the sleep methods and the none sleep methods
that I believe is a symptom/display of the unexpectedly high CPU usage when the
process should be sleeping.
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-31-generic 3.2.0-31.50
ProcVersionSignature: Ubuntu 3.2.0-31.50-generic 3.2.28
Uname: Linux 3.2.0-31-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu13
Architecture: amd64
ArecordDevices:
**** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: STAC92xx Analog [STAC92xx Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: dlj 1778 F.... pulseaudio
Card0.Amixer.info:
Card hw:0 'PCH'/'HDA Intel PCH at 0xc0800000 irq 50'
Mixer name : 'Intel CougarPoint HDMI'
Components : 'HDA:111d76e0,103c1793,00100102
HDA:80862805,103c1793,00100000'
Controls : 22
Simple ctrls : 10
Date: Fri Sep 28 20:57:35 2012
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64
(20120823.1)
MachineType: Hewlett-Packard HP Pavilion dm4 Notebook PC
ProcEnviron:
TERM=xterm
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-31-generic
root=UUID=162256F02256D479 loop=/hostname/disks/root.disk ro quiet splash
vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-3.2.0-31-generic N/A
linux-backports-modules-3.2.0-31-generic N/A
linux-firmware 1.79.1
SourcePackage: linux
StagingDrivers: rts_pstor mei
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 01/17/2012
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: F.08
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: 1793
dmi.board.vendor: Hewlett-Packard
dmi.board.version: 41.1C
dmi.chassis.asset.tag: Chassis Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Hewlett-Packard
dmi.chassis.version: Chassis Version
dmi.modalias:
dmi:bvnHewlett-Packard:bvrF.08:bd01/17/2012:svnHewlett-Packard:pnHPPaviliondm4NotebookPC:pvr068E100002204710000622100:rvnHewlett-Packard:rn1793:rvr41.1C:cvnHewlett-Packard:ct10:cvrChassisVersion:
dmi.product.name: HP Pavilion dm4 Notebook PC
dmi.product.version: 068E100002204710000622100
dmi.sys.vendor: Hewlett-Packard
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug precise running-unity staging
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https://bugs.launchpad.net/bugs/1058854
Title:
High CPU usage of CFS
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