On Fri, Oct 20, 2023 at 02:42:38PM +0200, daggs wrote:
Greetings, I have a windows 11 vm running on my Gentoo using libvirt (9.8.0) + qemu (8.1.2), I'm passing almost all available resources to the vm (all 16 cpus, 31 out of 32 GB, nVidia gpu is pt), but the performance is not good, system lags, takes long time to boot.
There are couple of things that stand out to me in your setup and I'll assume the host has one NUMA node with 8 cores, each with 2 threads as, just like you set it up in the guest XML. * When you give the guest all the CPUs the host has there is nothing left to run the host tasks. You might think that there "isn't anything running", but there is, if only your init system, the kernel and the QEMU which is emulating the guest. This is definitely one of the bottlenecks. * The pinning of vCPUs to CPUs is half-suspicious. If you are trying to make vCPU 0 and 1 be threads on the same core and on the host the threads are represented as CPUs 0 and 8, then that's fine. If that is just copy-pasted from somewhere, then it might not reflect the current situation and can be source of many scheduling issues (even once the above is dealt with). * I also seem to recall that Windows had some issues with systems that have too many cores. I'm not sure whether that was an issue with an edition difference or just with some older versions, or if it just did not show up in the task manager, but there was something that was fixed by using either more sockets or cores in the topology. This is probably not the issue for you though.
after trying a few ways to fix it, I've concluded that the issue might be related to the why the hdd is defined at the vm level. here is the xml: https://bpa.st/MYTA I assume that the hdd sits on the sata ctrl causing the issue but I'm not sure what is the proper way to fix it, any ideas?
It looks like your disk is on SATA, but I don't see why that would be an issue. Passing the block device to QEMU as VirtIO shouldn't cause that much of a difference. Try measuring the speed of the disk on the host and then in the VM maybe. Is that SSD or NVMe? I presume that's not spinning rust, is it.
Thanks, Dagg.
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