CPU and Processor Time Counter
Read this introduction to computer performance and information about computing processor time. In most programming languages, there is a process to measure elapsed time, such as time() in C. By subtracting the time at the beginning of a process from the time at the end you get the total time for a particular operation. Usually short operations are put in a loop that repeats the operation a sufficient number of times to get an accurate measurement.
CPU time: The count of cycles, also known as clockticks, forms the basis for measuring how long a program takes to execute.
How do you measure Execution Time?
|CPU Time||Running which code|
|Kernel (Sys) Time||Operating system code - the time of CPU spent on the kernel (system) code only within the given process - other processes and the time when our process is blocked are not included.|
|User Time||Time CPU spends running the program code (ie CPU time spent on non-kernel (user-mode) code only within the given process – so other processes and the time when our process is blocked are not included.).|
|Total time||User + Kernel|
|Real Time||Wall clock (total elapsed time) (can be lower than total time because of parallelism or longer because of wait) - user-perceived time it took to execute the command – from the start to the end of the call, including time slices used by other processes and the time when our process is blocked (e.g. I/O waiting)|
To see CPU time, you can look at the performance tab of a process in Process Explorer:
Red in the CPU usage graph indicates CPU usage in kernel-mode whereas green is the sum of kernel-mode and user-mode execution.
A data collector set can be configured via logman.exe to log the “% Processor Time” counter in the “Processor Information” object for this purpose.
Every conventional processor has a clock with a fixed cycle time (or clock rate). At every CPU cycle, an instruction is executed.
Putting it all together:
CPI is somewhat artificial (since it is computed from the other numbers) but it seems to be intuitive and useful.
Use dynamic instruction count (#instructions executed), not static (#instructions in compiled code)
Performance is the response time distributed through the request lifetime.
Busy vs Wait
The busy vs. wait percentage shown in monitoring tool is generally:
Units (MHz to ns)
Rate is often measured in MHz (millions of cycles per second)
Time is often measured in ns (nanoseconds)
Source: DataCademia, https://datacadamia.com/counter/resource/system/cpu/time
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