HP Caliper User's Guide

Table B-19 Information in icache Measurement Reports (continued)
DescriptionColumn
Routine from your application.Function
Source file associated with a function.File
The column contains one of these:
• A source-code line number for rows showing statements
• An instruction slot number for rows showing instructions not on a bundle
boundary
• A source-code column number followed by an offset from the beginning address
of a function for rows showing instructions on a bundle boundary
Column and line numbers are preceded by “~” when they are approximate due to
optimization.
Line |
Slot |
Col,Offset
The column contains either a source statement, preceded by “>”, or a disassembled
instruction. Statements that are out of order due to optimization are preceded by “*>”.
>Statement |
Instruction
Function Details
A cache line is the smallest unit of data that is transferred at one time between main
memory and the instruction cache. On Itanium 2 systems, cache lines are 64 bytes (12
instructions). Cache lines are the finest level of granularity available in icache
measurement reports.
These reports show data associated with a cache line on the same row as the first
instruction of the cache line. Each set of instructions that make up a cache line are
preceded and followed by a row of dashes (“- - - -”). The cache lines shown might not
be contiguous.
Non-contiguous cache lines are separated by a row of tildes (“~ ~ ~ ~”).
How Instruction Cache Metrics Are Obtained
HP Caliper obtains instruction cache metrics from the processor's performance
monitoring unit (PMU).
Exact counts are obtained from the PMU's set of performance monitor configuration
(PMC)/performance monitor data (PMD) register pairs. Sampled instruction cache
metrics are obtained from the PMU's instruction event address register (I-EAR). Both
sets of metrics focus on the L1 cache.
HP Caliper takes samples every Nth instruction cache miss, where N is defined in the
icache measurement configuration file in the HP Caliper home directory config/)
subdirectory. At each sample point, HP Caliper records both the cache line that resulted
in an instruction cache miss and the latency, number of clock cycles, incurred by the
miss. You can override the value in the measurement configuration file by using the
-s option.
280 Descriptions of Measurement Reports