Advanced POWER Virtualization on IBM System p5 - Previous ...

#
done
fi
exit
end
5.5 Monitoring a virtualized environment
Oscar Wilde once said “The truth is rarely pure and never simple”. This
statement could be applied to monitoring system resource usage in a virtualized
environment. In these environments, the amount of resources owned by a
partition can change on-the-fly and this presents new challenges to both the
developers of performance tools and those trying to interpret the results.
This section starts with some theory on how tools measure virtual resource
usage before diving into the practicalities of using the tools and presenting some
of the new AIX 5L performance-related commands.
5.5.1 Ask the right questions
Here are few of the questions that must be answered when designing
performance monitoring tools in a virtualized environment. In many cases, there
are several correct answers.
When using SMT, how do you measure the resource usage of the two logical
processors? Is a logical processor that is using 50 percent of the physical
processor 100% busy? When is an uncapped virtual-processor 100 percent
busy? What should be reported if the configuration changes during the
monitoring?
To help give an answer to these questions and others, the <strong>POWER</strong>5 family of
processors implements a new performance-specific register called the Process
Utilization Resource Register (PURR). The PURR tracks the real processor
resource usage on a per thread or per partition level. The AIX 5L performance
tools have been updated in AIX 5L V5.3. It had been modified to show these new
statistics.
Chapter 5. System management 321