← Back to team overview

kernel-packages team mailing list archive

  1. kernel-packages team
  2. Mailing list archive
  3. Message #135667

[Bug 1497447] [NEW] cgroup cpuacct.stats underreports cpu usage

  Thread Previous • Date Previous • • Thread Next 
Public bug reported:

I've reproduced this in both 3.8 and 3.13.0-64.104 kernel versions, on
both VirtualBox and in AWS.

>From doing some experiments, it seems like the more threads running in
the cgroup, the more cpuacct.stats underreports.  If I run this example
with one thread, both top and cpuacct.stat report 100% cpu.

To reproduce:
Run this python script in the background:
python << EOF
import threading
import time

def do_it():
  n = 0
  while True:
    n += 1

for n in range(0, 15):
  t = threading.Thread(target=do_it)
  t.start()

threading.Event().wait()
EOF

observe process CPU usage in top (depending on system  ~80 - 120%)
move into a cpuacct cgroup:

cd /sys/fs/cgroup/cpuacct
mkdir test
echo [pid] > cgroup.procs

Watch the change in cpuacct.stat:
cat cpuacct.stat && sleep 1 && cat cpuacct.stat

In my test top reported ~106% CPU while cpuacct.stat over 1 second
reported .61 (61%)

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.8.0-44-generic 3.8.0-44.66~precise1
ProcVersionSignature: Ubuntu 3.8.0-44.66~precise1-generic 3.8.13.25
Uname: Linux 3.8.0-44-generic x86_64
AlsaDevices:
 total 0
 crw-rw---T 1 root audio 116,  1 Sep 16 07:46 seq
 crw-rw---T 1 root audio 116, 33 Sep 16 07:46 timer
AplayDevices: Error: [Errno 2] No such file or directory
ApportVersion: 2.0.1-0ubuntu17.9
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CRDA: Error: [Errno 2] No such file or directory
Date: Fri Sep 18 13:16:32 2015
HibernationDevice: RESUME=UUID=a9509269-b6ce-4739-b237-d1fc96077c82
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
IwConfig: Error: [Errno 2] No such file or directory
Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99
MachineType: innotek GmbH VirtualBox
MarkForUpload: True
PciMultimedia:
 
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 VESA VGA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.8.0-44-generic root=/dev/mapper/hostname-root ro quiet
RelatedPackageVersions:
 linux-restricted-modules-3.8.0-44-generic N/A
 linux-backports-modules-3.8.0-44-generic  N/A
 linux-firmware                            1.79.18
RfKill: Error: [Errno 2] No such file or directory
SourcePackage: linux-lts-raring
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH

** Affects: linux-lts-raring (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug precise qa-kernel-lts-testing

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux-lts-raring in Ubuntu.
https://bugs.launchpad.net/bugs/1497447

Title:
  cgroup cpuacct.stats underreports cpu usage

Status in linux-lts-raring package in Ubuntu:
  New

Bug description:
  I've reproduced this in both 3.8 and 3.13.0-64.104 kernel versions, on
  both VirtualBox and in AWS.

  From doing some experiments, it seems like the more threads running in
  the cgroup, the more cpuacct.stats underreports.  If I run this
  example with one thread, both top and cpuacct.stat report 100% cpu.

  To reproduce:
  Run this python script in the background:
  python << EOF
  import threading
  import time

  def do_it():
    n = 0
    while True:
      n += 1

  for n in range(0, 15):
    t = threading.Thread(target=do_it)
    t.start()

  threading.Event().wait()
  EOF

  observe process CPU usage in top (depending on system  ~80 - 120%)
  move into a cpuacct cgroup:

  cd /sys/fs/cgroup/cpuacct
  mkdir test
  echo [pid] > cgroup.procs

  Watch the change in cpuacct.stat:
  cat cpuacct.stat && sleep 1 && cat cpuacct.stat

  In my test top reported ~106% CPU while cpuacct.stat over 1 second
  reported .61 (61%)

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: linux-image-3.8.0-44-generic 3.8.0-44.66~precise1
  ProcVersionSignature: Ubuntu 3.8.0-44.66~precise1-generic 3.8.13.25
  Uname: Linux 3.8.0-44-generic x86_64
  AlsaDevices:
   total 0
   crw-rw---T 1 root audio 116,  1 Sep 16 07:46 seq
   crw-rw---T 1 root audio 116, 33 Sep 16 07:46 timer
  AplayDevices: Error: [Errno 2] No such file or directory
  ApportVersion: 2.0.1-0ubuntu17.9
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  CRDA: Error: [Errno 2] No such file or directory
  Date: Fri Sep 18 13:16:32 2015
  HibernationDevice: RESUME=UUID=a9509269-b6ce-4739-b237-d1fc96077c82
  InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
  IwConfig: Error: [Errno 2] No such file or directory
  Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99
  MachineType: innotek GmbH VirtualBox
  MarkForUpload: True
  PciMultimedia:
   
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB: 0 VESA VGA
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.8.0-44-generic root=/dev/mapper/hostname-root ro quiet
  RelatedPackageVersions:
   linux-restricted-modules-3.8.0-44-generic N/A
   linux-backports-modules-3.8.0-44-generic  N/A
   linux-firmware                            1.79.18
  RfKill: Error: [Errno 2] No such file or directory
  SourcePackage: linux-lts-raring
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 12/01/2006
  dmi.bios.vendor: innotek GmbH
  dmi.bios.version: VirtualBox
  dmi.board.name: VirtualBox
  dmi.board.vendor: Oracle Corporation
  dmi.board.version: 1.2
  dmi.chassis.type: 1
  dmi.chassis.vendor: Oracle Corporation
  dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
  dmi.product.name: VirtualBox
  dmi.product.version: 1.2
  dmi.sys.vendor: innotek GmbH

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-lts-raring/+bug/1497447/+subscriptions

Follow ups

  Thread Previous • Date Previous • • Thread Next