Locality-Optimized Resource Alignment

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• terminating a major application or completing a backup
• dynamic platform operation such as online cell activation
The simplest way to use the command is to invoke it with no arguments:
loratune
More details are available in the man page.
Benefits
Performance
LORA reduces average memory access latency times in comparison to the interleaved memory mode.
The magnitude of the reduction depends on the memory reference pattern and the number of localities
in the partition. When processors spend less time waiting for memory references to be satisfied, all
aspects of application performance improve. Typically, response times decrease and throughput
increases at the same time that processor utilization drops. A rough estimate of the performance
benefit is 20%. As
Table 1 indicates, the benefit is greater for larger partitions.
Cost
LORA makes processors operate more efficiently, which can be realized as an increase in
performance. Alternatively, the increased efficiency can be used to reduce the number of processor
cores allocated to an application workload. This reduces the hardware provisioning cost, and may
also save on the cost of software licenses as well. The LORA configuration guidelines sometimes
recommend an increase in the amount of memory, which may offset some of the cost savings due to
increased processor efficiency.
Power management
Power management has strong synergy with LORA. By its nature, LORA groups hardware
components by their physical locality. These localities often match power domains, which gives
opportunities for power savings at times of low hardware utilization.
The newest Itanium processors have multiple cores per socket, and have low-power modes. The
greatest power savings are realized when all cores in a socket enter the low-power mode, as
compared to having single cores in multiple sockets in the low-power mode. LORA tends to group
cores by their proximity, increasing the chances that an entire socket can enter low-power mode when
an application is experiencing a light load.
Summary
Locality-Optimized Resource Alignment is a framework for improving performance on HP servers with
a Non-Uniform Memory Architecture, introduced with HP-UX 11i v3 Update 3 and enhanced in
subsequent updates. This paper explains the circumstances in which LORA is beneficial and gives
guidelines for deployment in those cases. When LORA is used with commercial applications,
performance is about 20% better than the SMP interleaved memory configuration. LORA simplifies
server configuration by presenting uniform configuration guidelines. LORA dovetails nicely with
power management strategies.