Every counter belongs to a counter class. The class determines which filters are available for the counter.
Streamline supports the following basic classes of counters:
- Absolute counters, for example Memory:
Free, report the current, absolute value. Use the
minimumfilters with absolute counters.
- Delta counters, for example Clock:
Cycles, report the number of occurrences since the last
measurement. The exact time when the data occurs is unknown, so data is
interpolated between timestamps. Use the
hertzfilters with delta counters.
- Incident counters, for example Kmem: kmalloc, are the same as delta counters, except the exact time is known when the data occurs, so no interpolation is calculated.
- Activity counters, for example Contention:
Wait, report changes in processor activity or state. Use the
averagefilter with activity counters.
For counters other than Activity counters, the data is calculated for 1ms resolution even in a high-resolution report. The high resolution zoom levels for these counters show interpolated values based on the 1ms data.
The following figure illustrates how the same data received from gator appears differently, depending on the counter class. In each case, the value 10 occurs at the 4.999ms timestamp, and the value 6 occurs at 6.999ms. The red lines shows the counter value at 1ms time intervals.
NoteIn the delta counter chart, the value of 10 at 4.999ms is amortized from 5ms back to 0ms, because there is no other value, so its value is 2 for that period. The value of 6 at 6.999ms is amortized from 7ms back to 5ms, which is when the last value was received, so its value is 3 for that period.
Figure 5-42 Counter classes