It may receive an event that would normally cause it to awaken the VCPU however if the system is overcommitted, it may take much longer for the VCPU to be woken up. When a guest idles a VCPU, that VCPU will be put on the scheduler queue. However, it is not a general indication of overcommit. The guest OS can then use that information to correct its usage information and preserve fairness. ![]() Steal time is simply a way to tell a guest that it was pre-empted. This affects fairness and can cause lots of bad things. This means that if a guest is pre-empted, then CPU usage reporting in the guest becomes horribly wrong with some processes having much higher reported usage than they actually got. ![]() When a hypervisor needs to pre-empt a running guest, without steal time, when the hypervisor eventually resumes that guest, as far as the guest can tell, the process that was running when the whole guest was pre-empted had run the entire time. This analysis of steal time is not entirely correct.
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