Memory usage and Xen hypervisor
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Hello everyone !
I have a question about memory in general with XCP-ng (pure curiosity).
I have my homelab host with 64GB of RAM, so the Dom0 memory is about 4.2GB, all fine (and it's correct according calculation provided by Citrix : https://docs.citrix.com/en-us/citrix-hypervisor/memory-usage.html)
But when I looked in Xen Orchestra memory stats graphs, it indicate me that 5.28 GB is used on the host (with no vm running). Using the
xeCLI, I got the same information (using the commands provided on the link above).Is there some kind of "overhead" or memory reservation by the Xen hypervisor itself under the hood (or something else) ? I can't find any information about this.
IIRC ESXi has a more or less similar behavior where it reserve some memory for it's own operations, dunno if it's the same here with XS/XCP-ng.
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That's because there's no really a "host", but Xen + dom0.
The amount reported in the Citrix Hypervisor section in XenCenter includes the memory used by the control domain (dom0), the Xen hypervisor itself, and the crash kernel. Therefore, the amount of memory reported in XenCenter can exceed these values. The amount of memory used by the hypervisor is larger for hosts using more memory.
https://docs.citrix.com/en-us/citrix-hypervisor/memory-usage.html
You can also do a
xe host-param-list uuid=<your host> | grep -i memory, you have the detail on the "overhead". -
@olivierlambert I must be blind, no other explaination....
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No worries
