kernel-packages team mailing list archive

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

Some things (like the hardware of the host) we get through apport-collect. It would be good to get a better understanding of the guest usage. Like how many guests, how much memory they get, how many vcpus. virtio disks and network and how are the guests connected to the network (NAT bridge, transparent bridge, openvswitch?). Are vdisk using raw images or qcov2, image files or partitions or logical volumes. 
Maybe then we can also replicate the issue in a test environment. Up to now I am not sure I ever was able to see the same issue or not. Oh and was there a specific stat or combination of stats that hints this is happening. Laggy terminal is hard to test for in some scripted way.

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https://bugs.launchpad.net/bugs/1344430

Title:
  10-15% iowait on kvm instances on Ubuntu 14.04

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  After upgrading from Ubuntu 12.04 to Ubuntu 14.04 we began seeing
  10-15% iowait on kvm guests.  The guests had little to no load and yet
  the shell was laggy and commands took forever to respond (assuming you
  could even type them)

  # uname -a
  Linux kvm-andromeda 3.13.0-29-generic #53-Ubuntu SMP Wed Jun 4 21:00:20 UTC
  2014 x86_64 x86_64 x86_64 GNU/Linux

  # kvm --version
  QEMU emulator version 2.0.0 (Debian 2.0.0+dfsg-2ubuntu1.1), Copyright (c)
  2003-2008 Fabrice Bellard

  I posted to Ubuntu Server and they suggested that I upgrade my kernel
  version.

  Relevant Mailing List discussion:

  https://lists.ubuntu.com/archives/ubuntu-server/2014-July/006925.html

  After installing a 3.14 kernel the performance returned to normal.

  kvm-andromeda:~# uname -a
  Linux kvm-andromeda 3.14.1-031401-generic #201404141220 SMP Mon Apr 14 16:21:48 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
  --- 
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  DistroRelease: Ubuntu 14.04
  Package: linux (not installed)
  ProcEnviron:
   TERM=screen
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  Tags:  trusty
  Uname: Linux 3.14.1-031401-generic x86_64
  UnreportableReason: The running kernel is not an Ubuntu kernel
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: root
  _MarkForUpload: True

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