July 18, 20196 yr 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.
July 18, 20196 yr You could just not pin any cores (or overlap the pinning) to each VM and let them duke it out themselves
July 18, 20196 yr Author 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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