On 1/17/23 15:15, Martin Kletzander wrote: > On Tue, Jan 17, 2023 at 01:44:44PM +0100, Michal Privoznik wrote: >> We have virDomainGetCPUStats() API which offers querying >> statistics on host CPU usage by given guest. And it works in two >> modes: getting overall stats (@start_cpu == -1, @ncpus == 1) or >> getting per host CPU usage. >> >> For the QEMU driver it is implemented by looking into values >> stored in corresponding cpuacct CGroup controller. Well, this >> works for system instances, where libvirt has permissions to >> create CGroups and place QEMU process into them. But it does not >> fly for session connection, where no CGroups are set up. >> >> Fortunately, we can do something similar to v8.8.0-rc1~95 and use >> virProcessGetStatInfo() to fill the overall stats. Unfortunately, >> I haven't found any source of per host CPU usage, so we just >> continue throwing an error in that case. >> > > Looks ok, but there's one thing that's bothering me a bit. On non-Linux > platforms this API would start to work and returning zeros. Could that > be fixed somehow in a nice fashion or should I treat that as a non-issue? Good point, I've never realized that non-Linux version of virProcessGetStatInfo() doesn't fail. Let me post a v2 in which I'll change the function to return error followed by this patch. Michal
