Workload requirements
Not all workloads are considered for optimization. The workload must meet certain requirements to benefit from the optimization.
General requirements
All thresholds are set internally by ASO and cannot be changed. For any workload to be considered for optimization, it must meet the following requirements:- Minimum age
- Workloads must be a certain age to be considered for a cache affinity optimization or a memory affinity optimization. The age requirement ensures that there is enough history to use as a basis to determine whether a change to the settings is required.
- Priority order
- The ASO daemon runs with a fixed scheduler priority. If the scheduler priority of a workload, or any of its threads, is higher than the scheduler priority of the ASO daemon, the workload is not optimized.
- Minimum processor utilization
- Workloads that have processor utilization lesser than the minimum level required to qualify for optimization are not changed.
Specific optimization requirements
AIX Dynamic System Optimizer also has requirements that do not apply to all of the optimizations.- Cache affinity optimization and memory affinity optimization
- ASO is designed to improve performance of workloads that have a long-term existence, are
multithreaded, and have stable processor utilization. The minimum time that a workload must exist
varies according to the type of optimization. The performance gain is higher for workloads that have
a high amount of communication between the threads in the workload.
- Multithreaded or Multiprocess
- Workloads must contain multithreaded processes or multiple single-threaded processes that are using the same shared memory.
- Free of Workload Manager (WLM) tiers and minimum limits classifications
- Workloads that are classified with tiers or have minimum limits set by the Workload Manager are
not optimized. If the processor capacity of the system is fully used, ASO does not optimize
processes that belong to classes with specific shares.Note: Workload Partition (WPAR) workloads (which implicitly use WLM) can be optimized by ASO if minimum processor limits are not specified.
- User-specified placement
- When you explicitly set the location of workloads by using attachments like bindprocessor, resource set (RSET) (Real, Partition, or Exclusive RSETs), and Scheduler Resource Affinity Domain (SRAD), those workloads are not eligible for ASO optimization. Although ASO does not affect these workloads, the AIX® operating system continues to enforce the resource constraints as normal. Any attempts to place such a restriction on a workload that is being optimized by ASO causes ASO to undo its optimization, and ASO allows your restriction to take priority.
- Large page optimization
- The ideal workload is one that uses large System V memory regions.
Examples of these workloads are a database with a large shared memory
region or Java™ programs that
use a large heap. Workloads can be either multithreaded or a group
of single threaded processes that are attached to the same shared
memory region.
- Fully populated segments
- Only 4 KB and 64 KB regions within a shared memory segment that are fully populated are considered for an upgrade to the 16 MB page size.
- Memory footprint minimum
- The memory footprint of the workload must be greater than the minimum value, measured in gigabytes.
- Data stream prefetch optimization
- Workloads with large memory footprints, high processor utilization,
and high-context switch rates are often candidates for this optimization.
Workloads must use System V shared memory to be considered for the
data stream prefetch optimization. Workloads are either multi-threaded
or a group of single-threaded processes. This optimization is disabled
if the Data Stream Control Register (DCSR) is set manually at the
system level by using the dscrctl command.
- Memory footprint minimum
- The memory footprint of the workload must be greater than the minimum value, measured in gigabytes.