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Dynamic Resources

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I have a host machine with 48Gb or RAM, and 12 logical cores. I have 2 VMs that are used constantly so I've given each of them 6 cores and about 14Gb of RAM. Sometimes though, 1 of the 2 VMs isn't being used and having 6 cores sitting idle is such a waste. How can I setup my system to give either VM all 12 cores (and maybe a lot more RAM) when they are available, but to split up the cores evenly when one of the 2 VMs needs them?

I've done some reading on libvirt.org and tried Googling "Dynamic CPUs in KVM" and tried a few things but there always seems to be a problem.

I've installed Virt-manager and tried a topology with 12 sockets 1 CPU and 1 thread. Both VMs 'function' fine until I start running any major tasks on both of them, then they'll just lock up.

I reverted back to just assigning 6 cores to each VM via Unraid VM panel for now so posting my XML 'as is' now wouldn't be all that helpful.

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You could just not pin any cores (or overlap the pinning) to each VM and let them duke it out themselves

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I believe I tried this already, but it just caused crashes. I was thinking something like, maybe give each vm only 6 "pinned" CPUs.. like vm A gets cpus 0-5 and vm b gets 6-11 but then just tell each VM to have 12 CPUs? The point would be 6 dedicated CPUs to each VM + 6 more to each when ever those are free...

IDK if this can be done as my knowledge and experience with VMs is mostly based on the top 5-10 results in a Google search.. lol.

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