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[Launchpad Bug Tracker <1023214@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/1023214

Title:
  bogus utime and stime in /proc/<PID/stat

Status in “linux” package in Ubuntu:
  Expired

Bug description:
  I administer a large number of servers, and I have this problem only
  with Ubuntu 10.04 LTS: I run a server under normal load (say load
  average 3.0 on an 8-core server). The "top" command shows processes
  taking certain % of CPU that cause this load average: say

  
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  11008 mysql     20   0 25.9g  22g 5496 S   67 76.0 643539:38 mysqld

  ps -o pcpu,pid -p11008
  %CPU   PID
  53.1 11008

  everything is consistent.

  The all of the sudden, the process causing the load average disappears
  from "top", but the process continues to run normally (albeit with a
  slight performance decrease), and the system load average becomes
  somewhat higher. The output of ps -o pcpu becomes bogus:

  
  # ps -o pcpu,pid -p11008
  %CPU      PID
  317910278 1587

  
  This happened to at least 5 different severs (different brand new IBM System X hardware), each running different software: one httpd 2.2, one mysqld 5.1, and one Twisted Python TCP servers. Each time the kernel was between 2.6.32-32-server and 2.6.32-40-server. I updated some machines to 2.6.32-41-server, and it has not happened on those yet, but the bug is rare (once every 60 days or so).

  This is from an affected machine:

  Code:
  top - 10:39:06 up 73 days, 17:57,  3 users,  load average: 6.62, 5.60, 5.34
  Tasks: 207 total,   2 running, 205 sleeping,   0 stopped,   0 zombie
  Cpu(s): 11.4%us, 18.0%sy,  0.0%ni, 66.3%id,  4.3%wa,  0.0%hi,  0.0%si,  0.0%st
  Mem:  74341464k total, 71985004k used,  2356460k free,   236456k buffers
  Swap:  3906552k total,      328k used,  3906224k free, 24838212k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  805 root      20   0     0    0    0 S    3  0.0   1493:09 fct0-worker
  982 root      20   0     0    0    0 S    1  0.0 111:35.05 fioa-data-groom
  914 root      20   0     0    0    0 S    0  0.0 884:42.71 fct1-worker
  1068 root      20   0 19364 1496 1060 R    0  0.0   0:00.02 top

  Nothing causing high load is showing on top, but I have two highly
  loaded mysqld instances on it, that suddenly show crazy %CPU:

  
  #ps -o pcpu,pid,cmd -p1587
  %CPU   PID CMD
  317713124 1587 /nail/encap/mysql-5.1.60/libexec/mysqld
  and

  
  #ps -o pcpu,pid,cmd -p1624
  %CPU   PID CMD
  2802  1624 /nail/encap/mysql-5.1.60/libexec/mysqld

  
  Here are the numbers from

  # cat /proc/1587/stat
  1587 (mysqld) S 1212 1088 1088 0 -1 4202752 14307313 0 162 0 85773299069 4611685932654088833 0 0 20 0 52 0 3549 27255418880 5483524 18446744073709551615 4194304 11111617 140733749236976 140733749235984 8858659 0 552967 4102 26345 18446744073709551615 0 0 17 5 0 0 0 0 0

  The 14th and 15th numbers according to

  man proc and fs/proc/array.c are supposed to be:

  utime %lu Amount of time that this process has been scheduled in user mode, measured in clock ticks (divide by
  sysconf(_SC_CLK_TCK). This includes guest time, guest_time (time spent running a virtual CPU, see
  below), so that applications that are not aware of the guest time field do not lose that time from
  their calculations.

  stime %lu Amount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by
  sysconf(_SC_CLK_TCK).

  On a normal server, these numbers 13 orders of magnitude smaller and
  they are advancing by about 10 per sec. On a buggy server, these
  numbers are stuck at a ridiculously high value like
  4611685932654088833, and they are not changing.

  I noticed that this bug does not happen on 2.6.24-26-server , and
  there has been many changes in fs/proc/array.c between
  2.6.24-26-server and 2.6.32-32-server when this bug starting to occur.

  ProblemType: Bug
  DistroRelease: Ubuntu 10.04
  Package: linux-server 2.6.32.40.47
  Regression: Yes
  Reproducible: No
  ProcVersionSignature: Ubuntu 2.6.32-40.87-server 2.6.32.57+drm33.23
  Uname: Linux 2.6.32-40-server x86_64
  NonfreeKernelModules: iomemory_vsl
  AlsaDevices: Error: command ['ls', '-l', '/dev/snd/'] failed with exit code 2: ls: cannot access /dev/snd/: No such file or directory
  AplayDevices: Error: [Errno 2] No such file or directory
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory
  Date: Tue Jul 10 17:33:10 2012
  Frequency: Once a month.
  InstallationMedia: Ubuntu-Server 10.04.2 LTS "Lucid Lynx" - Release amd64 (20110211.1)
  MachineType: IBM System x3550 M3 -[7944AC1]-
  PciMultimedia:

  ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-40-server root=UUID=ef643bc9-46ac-474d-bb00-4e0bfee77808 ro quiet
  ProcEnviron:
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: linux
  dmi.bios.date: 02/08/2011
  dmi.bios.vendor: IBM Corp.
  dmi.bios.version: -[D6E150CUS-1.11]-
  dmi.board.asset.tag: (none)
  dmi.board.name: 69Y5698
  dmi.board.vendor: IBM
  dmi.board.version: (none)
  dmi.chassis.asset.tag: none
  dmi.chassis.type: 23
  dmi.chassis.vendor: IBM
  dmi.chassis.version: none
  dmi.modalias: dmi:bvnIBMCorp.:bvr-[D6E150CUS-1.11]-:bd02/08/2011:svnIBM:pnSystemx3550M3-[7944AC1]-:pvr00:rvnIBM:rn69Y5698:rvr(none):cvnIBM:ct23:cvrnone:
  dmi.product.name: System x3550 M3 -[7944AC1]-
  dmi.product.version: 00
  dmi.sys.vendor: IBM

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