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[[Category:Virtualization]] <!-- do not copy into FWN issue -->
 
[[Category:Virtualization]] <!-- do not copy into FWN issue -->
 
  
 
{{Anchor|Virtualization}}
 
{{Anchor|Virtualization}}
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== 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 @virt-tools lists..
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@fedora-virt list.
  
 
Contributing Writer: [[User:Dale | Dale Bewley]]
 
Contributing Writer: [[User:Dale | Dale Bewley]]
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[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 ====
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==== Virt Status Report ====
[[MarkMcLoughlin|Mark McLoughlin]]
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[[JustinForbes|Justin Forbes]]
described<ref>http://www.redhat.com/archives/fedora-virt/2009-October/msg00119.html</ref>
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posted<ref>http://www.redhat.com/archives/fedora-virt/2009-December/msg00056.html</ref> a Fedora virtualization status report.
the default state of KSM<ref>http://fedoraproject.org/wiki/Features/KSM</ref> on Fedora systems.
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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.
"For Fedora 13, it'll be off by default in the kernel and the recommended
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way of switching it on is with 'chkconfig ksm on'"
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"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
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writing zero to {{filename|/sys/kernel/mm/ksm/run}}."
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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.
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<references />
To take advantage of KSM in Fedora 12, the <code>ksm</code> service must be enabled:
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<pre>
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sudo chkconfig ksm on
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</pre>
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[[MarkMcLoughlin|Mark McLoughlin]]
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==== RHEL and Fedora Virtualization Feature Parity ====
also noted<ref>http://www.redhat.com/archives/fedora-virt/2009-October/msg00112.html</ref>
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Robert Day wondered how the virtualization features<ref>http://www.redhat.com/virtualization/rhev/</ref> of Red Hat Enterprise Linux 5.4
The maximum number of pages which may be merged defaults to half of the system
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compared to Fedora 12.
memory, and may also be manually defined in {{filename|/etc/sysconfig/ksm}}.
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"Here's the logic we have in the init script<ref>http://gitorious.org/ksm-control-scripts/ksm-control-scripts</ref>:"
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<pre>
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  # unless KSM_MAX_KERNEL_PAGES is set, let ksm munch up to half of total memory.
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  default_max_kernel_pages () {
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      local total pagesize
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      total=`awk '/^MemTotal:/ {print $2}' /proc/meminfo`
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      pagesize=`getconf PAGESIZE`
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      echo $[total * 1024 / pagesize / 2]
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  }
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</pre>
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[[JustinForbes|Justin Forbes]]
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[[DanielBerrange|Daniel Berrange]]  
points out<ref>http://www.redhat.com/archives/fedora-virt/2009-October/msg00115.html</ref>
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explained<ref>http://www.redhat.com/archives/fedora-virt/2009-December/msg00040.html</ref>
"The limit to half of total memory is because ksm pages are unswappable at
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"The KVM based virtualization in RHEL-5.4 is not nearly so far behind
this time. To be fixed in a future kernel."
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Fedora as you might think. The {{package|libvirt}} mgmt stack in RHEL-5.4 was
 +
rebased to be near parity with [[Releases/11|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."
 +
 
 +
<references />
  
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
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====  ====
duplicates. At present only Qemu pages will be marked as such.
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<references />
As described in the kernel docs<ref>http://www.kernel.org/doc/Documentation/vm/ksm.txt</ref>,
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the effect of KSM system memory may be examined in {{filename|/sys/kernel/mm/ksm}}.
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"A high ratio of pages_sharing to pages_shared indicates good sharing, but
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a high ratio of pages_unshared to pages_sharing indicates wasted effort."
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 +
====  ====
 
<references />
 
<references />

Latest revision as of 18:09, 18 December 2009



Contents

[edit] Virtualization

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

Contributing Writer: Dale Bewley

[edit] Fedora Virtualization List

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

[edit] 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

[edit] 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 Package-x-generic-16.pnglibvirt 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


[edit]


[edit]