Meaning
Paravirtualized timing sources designed for the Kernel-based Virtual Machine provide guest operating systems with a stable and efficient way to read the host system time. Virtual machines often struggle with timekeeping because the hypervisor can pause their execution, leading to missed clock interrupts. Integration of kvm clock into the guest kernel allows the virtual machine to understand that it is running in a virtualized environment and to adjust its internal timers accordingly.
Guest Awareness
Awareness of the underlying hardware prevents the guest from experiencing the sudden jumps in time that often occur when using traditional hardware emulation. When kvm clock is active, the guest receives a stable time reference that is not subject to the same drift as an emulated real-time clock. This mechanism is essential for maintaining synchronization in distributed systems where multiple virtual machines must share a common timeline.
Interrupt Performance
Lower overhead is achieved because the guest reads time directly from a shared memory page rather than triggering an expensive exit to the hypervisor. Use of kvm clock reduces the processing power needed for timekeeping, leaving more cycles available for the actual application workload.
System Monotonicity
Time always moves forward without regression or large gaps, which is necessary for database logging and security protocols. Maintaining a monotonic clock ensures that events are recorded in the correct order across multiple virtualized instances.
