| Platform SDK: Performance Monitoring |
The table for each performance data time describes the components and formula used to perform the calculation. The following elements are used in the description.
| Element | Meaning |
|---|---|
| X | Many of the calculations use two data components, such as the raw data and the performance frequency. This describes one component. |
| Y | If a calculation is based on the raw data and another component, such as the performance frequency, this describes the second component |
| Data Size | The number of bytes of the raw data |
| Display Suffix | The result of the calculations may be displayed with a suffix that describes the formatted data units. Possible suffixes are as follows:
/Sec |
| Time base | If used in the calculation, the time base converts to units of seconds. If not, it indicates the units. |
| Calculation | Formula that describes how to convert the raw data and other components, such as performance frequency, to result in the formatted counter value. |
To help describe the calculations, the following symbols are used.
| Symbol | Definition |
|---|---|
| TB | Time base. If TB is not used in the calculation, then it indicates the units of the raw data. |
| B | The base value used for calculating performance data types that require base. See Performance Counter Bases. |
| 0,1,n | Subscript notation used when calculating with multiple samplings. A 0 refers to the oldest sampling, 1 refers to the more recent sampling, and n refers to the latest sampling. In the case of two data samplings, X1-X0 means to subtract the oldest data sampling value from the more recent data sampling. The symbol, n, may be used alone to indicate the number of samplings. For example, a raw count average is described as the sum of the values divided by the number of samplings, or (X0+X1+…+Xn)/n. |
The tables below also include a reference of the performance data value correlating to a symbol. The following table describes the values.
| Value | Comment |
|---|---|
| CounterData | The raw performance data value. |
| 100Ns | The calculation result is in 100-nanosecond units. |
| 100NsTime | The performance data sampling time in 100-nanosecond units. This is extracted from the PerfTime100nSec member of the PERF_DATA_BLOCK structure. |
| PerfTime | The sampling time of data collection. This value is taken from the PerfTime member of the PERF_DATA_BLOCK structure. However, if the performance data object is of type PERF_OBJECT_TIMER, then PerfTime is used. |
| PerfFreq | The sampling frequency performance data collection. It is used to convert PerfTime to seconds; for example, PerfTime/PerfFreq = seconds. This value is taken from the PerfFreq member of the PERF_DATA_BLOCK structure. However, if the performance data object is of type PERF_OBJECT_TIMER, then the PerfFreq member is used. |
Note The only performance data type that is of type PERF_OBJECT_TIMER is PERF_ELAPSED_TIME.