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{{Anchor|Virtualization}}
{{Anchor|Virtualization}}


== Virtualization ==
== Virtualization ==
In this section, we cover discussion of Fedora virtualization technologies on the
In this section, we cover discussion of Fedora virtualization technologies on the
@fedora-virt and @libvirt-list lists.
@fedora-virt list.


Contributing Writer: [[User:Dale | Dale Bewley]]
Contributing Writer: [[User:Dale | Dale Bewley]]
Line 13: Line 14:
[http://www.redhat.com/mailman/listinfo/fedora-virt fedora-virt list].
[http://www.redhat.com/mailman/listinfo/fedora-virt fedora-virt list].


==== KSM Tuning in Fedora 12 ====
==== Virt Status Report ====
[[MarkMcLoughlin|Mark McLoughlin]]
described<ref>http://www.redhat.com/archives/fedora-virt/2009-October/msg00119.html</ref>
the default state of KSM<ref>http://fedoraproject.org/wiki/Features/KSM</ref> on Fedora systems.
"For Fedora 13, it'll be off by default in the kernel and the recommended
way of switching it on is with 'chkconfig ksm on'"
"For Fedora [[Releases/12|12]], it's on by default in the kernel, 'chkconfig ksm on' just changes max pages and the only way of disabling it is by manually
writing zero to {{filename|/sys/kernel/mm/ksm/run}}."
 
At release of Fedora 12 the kernel will default to a maximum of 2000 merged memory pages. A future F12 kernel update to 2.6.32 will likely disable KSM by default.
To take advantage of KSM in Fedora 12, the <code>ksm</code> service must be enabled:
<pre>
sudo chkconfig ksm on
</pre>
 
[[MarkMcLoughlin|Mark McLoughlin]]
also noted<ref>http://www.redhat.com/archives/fedora-virt/2009-October/msg00112.html</ref>
The maximum number of pages which may be merged defaults to half of the system
memory, and may also be manually defined in {{filename|/etc/sysconfig/ksm}}.
"Here's the logic we have in the init script<ref>http://gitorious.org/ksm-control-scripts/ksm-control-scripts</ref>:"
<pre>
  # unless KSM_MAX_KERNEL_PAGES is set, let ksm munch up to half of total memory.
  default_max_kernel_pages () {
      local total pagesize
      total=`awk '/^MemTotal:/ {print $2}' /proc/meminfo`
      pagesize=`getconf PAGESIZE`
      echo $[total * 1024 / pagesize / 2]
  }
</pre>
 
[[JustinForbes|Justin Forbes]]
[[JustinForbes|Justin Forbes]]
points out<ref>http://www.redhat.com/archives/fedora-virt/2009-October/msg00115.html</ref>
posted<ref>http://www.redhat.com/archives/fedora-virt/2009-December/msg00056.html</ref> a Fedora virtualization status report.  
"The limit to half of total memory is because ksm pages are unswappable at
Justin pointed out F13 bugs<ref>http://fedoraproject.org/wiki/Virtualization_bugs</ref> now include Important and Pony classifications in addition to Blocker and Target.
this time.  To be fixed in a future kernel."
 
A second service, <code>ksmtuned</code>, may also be enabled.
Ksmtuned regulates how aggressively the system will attempt to merge pages.
Parameters such as how many pages to scan before sleeping and how long to
sleep may be configured in {{filename|/etc/ksmtuned.conf}}.
 
Memory pages must be flagged as mergable before KSM will scan them looking for
duplicates. At present only Qemu pages will be marked as such.
As described in the kernel docs<ref>http://www.kernel.org/doc/Documentation/vm/ksm.txt</ref>,
the effect of KSM system memory may be examined in {{filename|/sys/kernel/mm/ksm}}.
"A high ratio of pages_sharing to pages_shared indicates good sharing, but
a high ratio of pages_unshared to pages_sharing indicates wasted effort."


<references />
<references />


=== Libvirt List ===
==== RHEL and Fedora Virtualization Feature Parity ====
This section contains the discussion happening on the
Robert Day wondered how the virtualization features<ref>http://www.redhat.com/virtualization/rhev/</ref> of Red Hat Enterprise Linux 5.4
[http://www.redhat.com/mailman/listinfo/libvir-list libvir-list].
compared to Fedora 12.
 
==== Rewrite the QEMU monitor handling ====
[[DanielBerrange|Daniel Berrange]]
posted<ref>http://www.redhat.com/archives/libvir-list/2009-October/msg00644.html</ref> a
"patch series [which] rewrites the QEMU monitor handling almost completely.


The key theme here is to move from a totally synchronous way of
[[DanielBerrange|Daniel Berrange]]
interacting with the monitor, to a totally asynchronous way. This
explained<ref>http://www.redhat.com/archives/fedora-virt/2009-December/msg00040.html</ref>
allows " {{package|libvirt}} " to handle receipt & dispatch of asychronous events from
"The KVM based virtualization in RHEL-5.4 is not nearly so far behind
QEMU. For example a notification of a disk-full error, or VM state
Fedora as you might think. The {{package|libvirt}} mgmt stack in RHEL-5.4 was
change.  In the process of doing this re-factoring I have also
rebased to be near parity with [[Releases/11|Fedora 11]], and KVM in RHEL-5.4 is
dropped in basic support/infrastructure for the JSON based monitor."
also pretty close to that using what's best described as a hybrid of
kvm-83 and kvm-84."


<references />
<references />


==== Node device enumeration with udev ====
[[DaveAllan|Dave Allan]]
posted<ref>http://www.redhat.com/archives/libvir-list/2009-October/msg00731.html</ref>
"a fully functional version of the node device udev<ref>http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html</ref> based backend, incorporating all the feedback from earlier revisions." "...I have also included a patch removing the DevKit backend."


Also see FWN#146 <ref>http://fedoraproject.org/wiki/FWN/Issue146#Host_Device_Enumeration_API</ref> for some coverage of the host device enumeration API.
====  ====
<references />


====  ====
<references />
<references />

Latest revision as of 18:09, 18 December 2009



Virtualization

In this section, we cover discussion of Fedora virtualization technologies on the @fedora-virt list.

Contributing Writer: Dale Bewley

Fedora Virtualization List

This section contains the discussion happening on the fedora-virt list.

Virt Status Report

Justin Forbes posted[1] a Fedora virtualization status report. Justin pointed out F13 bugs[2] now include Important and Pony classifications in addition to Blocker and Target.

  1. ↑ http://www.redhat.com/archives/fedora-virt/2009-December/msg00056.html
  2. ↑ http://fedoraproject.org/wiki/Virtualization_bugs

RHEL and Fedora Virtualization Feature Parity

Robert Day wondered how the virtualization features[1] of Red Hat Enterprise Linux 5.4 compared to Fedora 12.

Daniel Berrange explained[2] "The KVM based virtualization in RHEL-5.4 is not nearly so far behind Fedora as you might think. The libvirt mgmt stack in RHEL-5.4 was rebased to be near parity with Fedora 11, and KVM in RHEL-5.4 is also pretty close to that using what's best described as a hybrid of kvm-83 and kvm-84."

  1. ↑ http://www.redhat.com/virtualization/rhev/
  2. ↑ http://www.redhat.com/archives/fedora-virt/2009-December/msg00040.html



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