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Home > FAQs > How do the CPU Metrics work and what is CPU Steal?

How do the CPU Metrics work and what is CPU Steal?

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Background Information

CPU Metrics can be viewed in the Monitoring tab of the RightScale Dashboard.



The cpu metrics are a combination of many CPU values and the "total" of those will add up to 100%.

user CPU used by user applications
nice CPU used to allocate multiple processes demanding more cycles than the CPU can provide
system CPU used by the operating system itself
interrupt CPU allocated to hardware interrupts
softirq CPU servicing soft interrupts
wait CPU waiting for disk IO operations to complete
steal* Xen hypervisor allocating cycles to other tasks
idle CPU not doing any work


*Steal time is the time that the CPU had something runnable, but the XEN hypervisor chose to run something else instead. 

Generally it is never possible for user processes to consume ALL of the CPU because as its load increases so does the load from other types of CPU usage listed above.  How a particular server uses its CPU depends on a number of factors but in general the real metric we use to determine CPU usage is the idle time.  This is the metric that alerts are based from.  The idle value is the amount of CPU left not doing any work.  If CPU has no idle time it is 100% in use - how that is allocated depends on the server architecture and the application.  In some cases it might be all User, System, and Steal.  If it is doing a massive database backup it might all be in wait.  It just depends.

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Last modified
21:25, 16 May 2013



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