[Qemu-devel] [Bug 524447] Re: virsh save is very slow

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On 2010-06-02T16:38:36+00:00 Cole wrote:

See https://bugs.launchpad.net/ubuntu/+source/qemu-
kvm/+bug/524447/comments/5

Apparently increasing the dd block size greatly increases the speed of
the domain save operation.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/524447/comments/6

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On 2010-06-07T17:56:00+00:00 Laine wrote:

commit 20206a4bc9f1293c69eca79290a55a5fa19976d5 in libvirt git changes
the dd blocksize to 1M. This decreased the time required for a save of a
suspended 512MB guest from 3min47sec to 56sec.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/524447/comments/8

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On 2010-06-10T12:19:33+00:00 Eric wrote:

An additional patch avoids the overhead of seeking to a 1M alignment:
https://www.redhat.com/archives/libvir-list/2010-June/msg00239.html

Reply at:
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/524447/comments/9

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On 2010-07-21T16:48:55+00:00 Daniel wrote:

This is included in 0.8.2. In addition upstream QEMU has identified &
fixed a flaw that had significant speed impact

Reply at:
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/524447/comments/15


** Changed in: libvirt
       Status: Unknown => Fix Released

** Changed in: libvirt
   Importance: Unknown => Medium

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https://bugs.launchpad.net/bugs/524447

Title:
  virsh save is very slow

Status in libvirt:
  Fix Released
Status in QEMU:
  Fix Released
Status in libvirt package in Ubuntu:
  Invalid
Status in qemu-kvm package in Ubuntu:
  Fix Released
Status in libvirt source package in Lucid:
  Won't Fix
Status in qemu-kvm source package in Lucid:
  Fix Released
Status in libvirt source package in Maverick:
  Won't Fix
Status in qemu-kvm source package in Maverick:
  Won't Fix
Status in qemu-kvm package in Debian:
  Fix Released

Bug description:
  ==================================
  SRU Justification:
  1. impact: 'qemu save' is slow
  2. how addressed: a patch upstream fixes the case when a file does not 
announce when it is ready.
  3. patch: see the patch in linked bzr trees
  4. TEST CASE: see comment #4 for a specific recipe
  5. regression potential:  this patch only touches the vm save path.
  ==================================

  As reported here: http://www.redhat.com/archives/libvir-
  list/2009-December/msg00203.html

  "virsh save" is very slow - it writes the image at around 1MB/sec on
  my test system.

  (I think I saw a bug report for this issue on Fedora's bugzilla, but I
  can't find it now...)

  Confirmed under Karmic.

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