HP Caliper User's Guide

alat Measurement Report Description
With the alat measurement, produced by the alat measurement configuration file,
HP Caliper measures and reports advance load address table (ALAT) misses.
The ALAT keeps track of speculative (that is, advance) loads. An excessive number of
ALAT compares that result in a failed advance load (an ALAT miss) can seriously
degrade performance. ALAT misses might point to inefficient use of data speculation
in assembly-level code or code generated by a compiler or virtual machine.
A miss ratio higher than 10 percent suggests a problem with how the program uses
data speculation.
The report shows two levels of information:
• Exact counts of ALAT metrics summed across the entire run of an application
• Sampled failed ALAT check instructions (chk.a or ld.c) that are associated with
particular locations in the measured application.
The report shows measured data by thread, load module, function, statement, and
instruction.
Command-line options allow you to control the amount of data reported, how the data
is sorted, and the number of statements and instructions reported for each sampled
program location.
To improve your results, try the following:
• When compiling from high-level code, change compiler options that affect data
speculation.
• When writing assembly code, tune the source code in the hot spots shown in the
report.
• When writing a compiler or a virtual machine, tune the code generator.
Example Command Line for Text Report
$ caliper alat -o reports/alat.txt ./wordplay thequickbrownfox
Example Command Line for CSV Report
$ caliper alat --csv csvout ./wordplay thequickbrownfox
alat Metrics Summed for Entire Run
This section describes the metrics summed over the entire run of your application under
HP Caliper.
Metrics for Integrity Servers Itanium 2 Systems
INST_CHKA_LDC_ALAT.ALL
The number of advance check load (chk.a) and
check load (ld.c) instructions that reached
retirement, including both integer and
floating-point instructions.
222 Descriptions of Measurement Reports