IBM Power System POWER7 Series, Optimization And Tuning Manual

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Chapter 4. AIX
89
– Workload age
Workloads must be at least 10 minutes of age to be considered.
Optimization time
When you test the effect of DSO on applications, it is important to run the tests for enough
time. The duration depends on the type of optimization that is being measured. For example,
in the case of large page optimization, there is a small increase in system usage (less than
2%) when the pages are being promoted. So, to see the benefit of large page optimization,
the test must be run for longer than the time taken to complete the promotions.
Here is the list of minimum test durations for each type of optimization. All of these times are
approximate, and only after the workload is stable.
Cache affinity optimization 30 minutes
Memory affinity optimization 1 hour
Large page optimization 12 hours for promoting 100 GB of shared memory
Memory prefetch optimization 30 minutes
4.2.4 The asoo command
The ASO framework is off by default in an AIX installation. The asoo command must be used
to enable the ASO framework. The command syntax is as follows:
asoo -po aso_active=1
4.2.5 Environment variables
Two environment variables are provided that control the behavior of ASO: ASO_ENABLED and
ASO_OPTIONS . These variables are examined at start time.
ASO_ENABLED
ASO_ENABLED provides an administrator with the ability to alter the default behavior of ASO
when you evaluate a workload for optimization.
Permitted values for this environment variable are:
򐂰 ALWAYS
:
ASO skips some of the primary eligibility checks for optimization eligibility, such as
age of workload and minimum CPU usage.
򐂰 NEVER
: ASO excludes this process from any optimization under all circumstances.
򐂰 Unsupported value
:
ASO optimizes the process as normal.
ASO_OPTIONS
ASO_OPTIONS provides an administrator with the ability to individually enable and disable
cache, memory affinity, large page, and memory prefetch optimization.