Understanding Duration Measurements - HP MC68040 User Manual

Chapter 7: Making Software Performance Measurements

Understanding duration measurements

Understanding duration measurements
Duration measurements provide a best-case/worst-case characterization of code
execution time. These measurements record execution times that fall within a set of
specified time ranges. The trace command is set up to store only the entry and exit
states of the module to be measured (for example, a C function or Pascal
procedure). The SPMT provides two types of duration measurements: module
duration and module usage.
Module duration measurements record how much time it takes to execute a
particular code segment (for example, a function in the source file).
Module usage shows how much of the execution time is spent outside of the
module (from exit to entry). This measurement gives an indication of how often
the module is being used.
Before you perform duration measurements, you should be aware of the prefetch
and recursion considerations associated with these measurements.
When using the SPMT to perform duration measurements, there should be only two
addresses stored in the trace memory: the entry address, and the exit address.
Prefetches or recursion can place several entry addresses before the first exit
address, and/or several exit addresses before the first entry address. Duration
measurements are made between the last entry address in a series of entry
addresses, and the last exit address in a series of exit addresses as shown in the
prefetch correction listing. All of the entry and exit addresses which precede these
last addresses are assumed to be unused prefetches, and are ignored during time
measurements.
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START - unused prefetch
START - unused prefetch
START - unused prefetch
START - START actually taken -
END - unused prefetch
END - unused prefetch
END - unused prefetch
END - END actually taken
START - unused prefetch
START - unused prefetch
START - unused prefetch
START - START actually taken -
END - unused prefetch
END - unused prefetch
Measure duration
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Measure duration