To analyze the processor utilization of your system you should focus on two counters - % Processor Time and Interrupts/sec. % Processor Time shows the percentage of overall processor utilization. If there is more than one processor on a system, a counter for each one is shown as well as the total (combined) value counter.
If % Processor Time averages a usage rate of over 50% for extended durations, you should first review other system counters to try and identify processes which may be improperly using the processing resource or alternatively consider upgrading the processor. Consistent utilization around the 50% range does not necessarily impair performance, however, the average processor utilization goes beyond 65% performance will almost certainly be impaired. If the system has multiple processors installed, you should use the % Total Processor Time counter to determine the average usage of all processors.
Interrupts/sec is useful for providing an overall guide of processor health. This counter indicates the number of device interrupts which the processor is handling per second. Similar to the Page Faults/sec counter this counter can show very high numbers (well into the thousands) without there being a significantly performance drag.
In general, conditions which could indicate a processor bottleneck include the below:
“Average of % Processor Time” is consistently beyond 60%–70%. Additionally, spikes which frequently occur frequently of 90% or greater can also indicate a bottleneck even if the average is below 60%–70%.
“Maximum of % Processor Time” is consistently beyond 90%.
“Average of the System Performance Counter; Context Switches/second” is consistently beyond 20,000.
“System Performance Counter; Processor Queue Length” is consistently higher than two.
The CPU tab in the Resource Monitor (below) gives a good high-level overview of processor activity. For more advanced monitoring of processor utilization you should use the Performance Monitor snap-in with the counters. discussed previously.