Bcc: Raghavendra K T <raghavendra.kt(a)linux.vnet.ibm.com&gt; Subject: Re: [libvirt] [RFC] exclusive vcpu-cpu pinning Reply-To: Raghavendra K T <raghavendra.kt(a)linux.vnet.ibm.com&gt; In-Reply-To: <53DA24CF.8030600(a)redhat.com&gt; * J?n Tomko <jtomko(a)redhat.com&gt; [2014-07-31 13:13:19]: Hi Jan, I am not familiar with libvirt internals, but eager to solve the problem (I also tried to solve the same problem, I had POC kernel solution which was rightly rejected because we could solve with userspace). Could we have a dedicated cpuset for vms (which asks for dedicated cpuset may be via xml tag? <description>dedicated</description>) [ This is very similar to what you have proposed ] suppose we have 2 vms of 8 vcpus (vm1 dedicated, vm2 non-dedicated) on a 16 pcpu machine, the modified cpuset cgroup hierarchy looks like this (for cpuset only): | root (cpuset.cpus = 0-15) | \_ machine (tasks = system tasks) (cpuset.cpus = 0-7, exclusive=1) \_ vm2.libvirt-qemu (cpuset.cpus = 0-7, exclusive=1) | \_ vm2.libvirt-qemu (cpuset.cpus = 8-15, exclusive=1) But as you have mentioned above libvirt will have to 1. modify the cpuset hierarchy behind systemd 2. move all the system tasks to machine (only for cpuset) 3. assign all the non dedicated cpuset to /machine hierarchy 4. assign dedicated/exclusive cpus to vms automatically. ofcourse we cannot have 100% of cpus to be dedicated and we will have to ensure that we do have some cpus left for system tasks/non dedicated vms etc. I see we could achieve above requirement with a userspace daemon, But I think libvirt way of solving would be ideal. Do you think the above solution is too intrusive? Please let us know your thoughts.