Re: Question regaring correct usage of CPU shares
On Fri, May 12, 2023 at 11:36:36AM +, mailing-libv...@posteo.de wrote: Hi there, Hi, sorry for the late answer. I have a question regarding the shares option of the cputune section. I want to illustrate my question with the following example. Let's assume I have two virtual machines like the following on four dedicated core with two threads each: VM1: 512 VM2: cputune> 512 Those two virtual machines I just mentioned won't interfere with one another since they are pinned to different cores. However I introduce another, third virtual machine, like this: VM3: 512 What I want is that VM1, VM2 and VM3 all receive half of the cores CPU time if congestion appears. My question is how the shares are That is what should, theoretically, happen, yes. And it does not matter if the value is 512, 7 or 2. calculated. Are they calculated on a per core basis? Meaning VM1 and No, they are set per-VM. VM3 use the first core so each will get half of the cores capacity when congestion appears, or are the shares calculated over all cores a virtual machine uses and I need to scale the amount of shares with increasing number of cores. What is the correct setting here so that all virtual machines in this example are guaranteed half of the capacity of each of their respective cores if congestion appears? The above is okay from this point of view. But it depends on the rest of your system. What scheduler you have, what are the other processes running, etc. You can have a look at the settings in cgroups (in v1 this is cpu.shares, in v2 I think that's cpu.weight) and see how they are set. Hope that helps, Martin signature.asc Description: PGP signature
Re: Cron jobs not working with virsh commands
On Fri, May 26, 2023 at 12:30:18PM +0200, Jeff Brown wrote: > Recently, while testing backup scripts, I happened to notice that 'virsh > snaphot-create-as . . .' has been failing with 'error: failed to get domain > '$DOMAIN'' when run through crontab. So I've been unwittingly backing up the > live, running, QCOW2 images for quite some time because scripts which run > fine when testing from CLI, fail to work as expected when run as a cron job. > > After much searching, I stumbled upon a related issue with the (obvious?) > simple solution almost hidden in the answers. You have to explicitly connect > to the local server with, e.g.: > > virsh -c qemu:///system snapshot-create-as . . . > > Humble apologies if I missed something I should have been aware of, but I > just thought it worthwhile mentioning here for anyone else searching for an > answer in the archives. If you don't specify a URI, then libvirt attempts to guess one based on what's installed, what's running and what user you're running the command as. Assuming libvirt qemu driver is installed & running, the latter point will be where you hit the problem Running as 'root' libvirt defaults to qemu:///system. Running as any non-root account, it defaults to qemu:///session Some more info here: https://libvirt.org/uri.html#default-uri-choice https://libvirt.org/drvqemu.html#connections-to-qemu-driver With regards, Daniel -- |: https://berrange.com -o-https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o-https://fstop138.berrange.com :| |: https://entangle-photo.org-o-https://www.instagram.com/dberrange :|
Cron jobs not working with virsh commands
Recently, while testing backup scripts, I happened to notice that 'virsh snaphot-create-as . . .' has been failing with 'error: failed to get domain '$DOMAIN'' when run through crontab. So I've been unwittingly backing up the live, running, QCOW2 images for quite some time because scripts which run fine when testing from CLI, fail to work as expected when run as a cron job. After much searching, I stumbled upon a related issue with the (obvious?) simple solution almost hidden in the answers. You have to explicitly connect to the local server with, e.g.: virsh -c qemu:///system snapshot-create-as . . . Humble apologies if I missed something I should have been aware of, but I just thought it worthwhile mentioning here for anyone else searching for an answer in the archives. Best regards, Jeff
