HP Caliper User's Guide

• %Dispersed Instr retired
This is a metric of dispatch efficiency, that is, the percentage of the instructions
that were dispersed that reached retirement. The number of instructions dispersed
will not equal the number reaching retirement primarily because of pipeline flushes
mainly due to mispredicted branches, traps, and interrupts. If the retirement ratio
is low, this is likely due to poor branch prediction. This can be confirmed with
using one of the branch prediction measurements (brpred or brpath). Other
possibilities include excessive speculation failures (cspec, dspec) and tlb misses.
• Software Limit - Dispersal ILP
This metric attempts to give some estimate of the compiler's ability to expose ILP
(instruction level parallelism). The metric is shown in two parts. The raw ILP
includes all instructions dispersed, including nop and instructions that will later
be predicated off. The effective ILP excludes all nops and predicated off
instructions, subject to the Itanium 2's predicated instruction semantics. This is
based on the number of instructions not dispersed due to explicit stops, as this is
directly controlled by the compiler.
• Combined Total - Dispersal ILP
This metric gives the overall dispersal ILP that the compiler, processor
implementation, and workload combination is providing. The metric is shown in
two parts. The raw ILP includes all instructions dispersed, including nops and
instructions that will later be predicated off. The effective ILP excludes all nops
and predicated off instructions, subject to the Itanium 2's predicated instruction
semantics.
314 Event Set Descriptions for CPU Metrics