HP Caliper User's Guide

dispersal Event Set
The dispersal event set provides a qualitative view of the parallelism that is available
as seen at instruction dispersal and provides information on the compiler's architectural
effectiveness. Instruction dispersal is the process of mapping instructions within bundles
to functional units. Architectural effectiveness is the extent to which the compiler is
able to exploit the available instruction level parallelism provided by the underlying
CPU implementation.
If you use this event set, the default is to make the measurements irrespective of CPU
operating state (that is, user, system, or interrupt states). By default, the idle state is
not included in the measurement. You can use command-line options to limit the scope
of the measurement. Specifically, you can:
• Limit measurement to a specific privilege level: -m
event_set[:all|user|kernel]
• Include idle: --exclude-idle False
• Exclude the interruption state: --measure-on-interrupts off
• Only measure the interruption state: --measure-on-interrupts only
Metrics Available from this Measurement
The following metrics are available from this event set. These descriptions do not take
into account any command-line options you might use.
The metrics are:
• Total Instr Dispersed
This is a count of the total number of instructions that were dispersed during the
sample observation period. The default mode will include all dispersal cycles.
• Total - Instructions not dispersed
This is a count of the number of instruction that were not dispersed during the
sample observation period due to either explicit or implicit stop bits. The default
of this measurement includes all dispersal cycles.
• Explicit - Instructions not dispersed
This is a count of the number of instructions that were not dispersed due to explicit
stop bits. Explicit stop bits are used to separate bundles (three instructions) within
a bundle group (two bundles of three instructions each) or to separate bundle
groups. Explicit stops bits can also be found within bundle-specific templates that
contain embedded stop bits, that is, M_II. The default mode will include all
dispersal cycles.
• Implicit - Instructions not dispersed
This is a count of the number of instructions that were not dispersed due to implicit
stop bits. Implicit stops are generated by the CPU when a CPU resource becomes
oversubscribed.
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