On 09/19/2018 05:57 AM, Joachim Wagner wrote:
While various cli options for memory backing have been introduced in 2014, the
virt-manager GUI doesn't offer any memory options other than current and
maximum allocation under open -> view -> details -> memory. The "locked"
memory backing option is probably the most easy to to understand and can have
huge impact when the host also acts as a file server or runs write-intense
applications. It would be useful to many users to have a check box for it in
the GUI.
Indications for a need for this check box:
* https://serverfault.com/questions/561446/how-can-i-keep-important-vms-in-memory-without-disabling-swap/
* https://serverfault.com/questions/477886/why-does-host-swap-out-vms-when-there-are-16gb-of-buffer-cache-and-swappiness
The other options may also be useful but typical users will require much more
guidance than offered in the libvirt documentation. I only start understanding
them reading <https://www.suse.com/documentation/sles-15/singlehtml/
article_vt_best_practices/article_vt_best_practices.html>.
This is one of those XML bits that's questionable to expose in the UI.
It's very important for some users, but it's 1) difficult to explain in
the UI, 2) has tricky operational caveats (see
https://libvirt.org/formatdomain.html#elementsMemoryBacking), 3) has a
limited audience who are already power users.
There's already a fairly easy command line way to enable this option,
once you know what it is:
virt-xml $VMNAME --edit --memorybacking locked=on
As the years go on and these types of requests seem to increase in
frequency, I'm thinking virt-manager really needs a raw XML editing
mode. Power users can make tweaks to the XML without leaving the UI, and
it will take a lot of pressure off us to implement/maintain/test power
user type options. That way the UI can refocus on the 90% case.
Hopefully I can get time to experiment with it by the end of the year
- Cole
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