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Performance Analysis Measurements
Model 1630A/D/G
LINKAGE OVERVIEW MEASUREMENTS
The Linkage Overview Measurement provides a histogram of the relative number of calls made between
modules, or the number of references made to devices or memory locations . A link is defined as two events
occurring one immediately after the other in the state memory . Up to eight of these events can be defined, in a
manner similar to the definition of resource terms . Up to eight link types, made up of two of any of these
defined events, may also be defined. The histogram chart for Linkage Measurement displays the percentage of
valid links for a defined link type versus the sum of the valid links found for all of the defined link types.
This measurement is useful in obtaining information about inter-module usage, or for obtaining information
about resource usage among several different modules. Therefore, this measurement might be used to
monitor the usage of an HP-113 communication chip by tasks performing system HP-113 input and output,
printer output, and mass storage input and output . The Linkage Histogram would provide information as to
which of the tasks was using the chip the most and which was using it the least . It would also provide
information as whether the tasks were using the chip more for input or for output transactions . The
measurement can also be useful in finding unexpected usage between modules by using the [other] and [any]
events .
Using this example, the events would be defined as the writes from and the reads to the HP-113 chip within the
individual modules . (In this case : System in, System out, Printer out, Disc in, Disk out.) Two more events would
be defined as the HP-113 routines which write to the chip, given as H_WRT (write) and H_RD (read) . To define
events, enter the event name in the label field of the "Events" section, and the address, data, and/or status
masks in the corresponding fields . More events can be added by pressing INSERT from anyone of these fields .
Figure 5-8 is the State Linkage Overview Trace Specification for this example measurement .
Link types for this example are: (System in) followed by (read), (System out) followed by (write), (Printer out)
followed by (write), (Disc in) followed by (read), and (Disc out) followed by (write) . Link types are defined by
entering the link type name in the label fields under the "Linkages" section . Events for the link types are
selected by using the NEXT and PREV keys to select from the predefined event labels, or to select an [any] or
[other]. [any] allows an event to be paired with any state following (therefore, it acts as a "don't care" event) .
[other] allows a valid link to its paired event when the link is not valid for any other link type with the same
paired event. Therefore, if a link type contained a leading event of [other] followed by a trailing event of
[H_RD], a link of some state followed by a state matching [HH_RD] would be a valid link forthis type only if its
leading state did not match any of the leading states of link types with trailing events of [H_RD] .
As in the State Label and Time Interval measurements, the logic analyzer runs in a continuous random sample
mode . When this example was run, the results shown in figure 5-9 were obtained . The results indicate that the
printer uses the HP-113 communication chip more than the other processes . If the effective transfer rate for
mass storage were low, these results might indicate that the printer process controls HP-113 chip more often
than the mass storage process, and might need its priority lowered.
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