Power Linux I/O Performance Tuning Guide version 2

Version 2 contains additional material for virtual adapters. It also addresses errata and feedback.

This document covers the following categories of tuning Linux for optimal performance:

• An architecture independent tuning method that applies generically to Linux irrespective of the platform on which it is run.
• IBM Power Systems servers specific tuning method that utilizes features that are available only with the Power architecture.

The performance tuning of a system is often a trade-off between choices. For instance,
tuning the system for low latency may reduce throughput. Hence, it is important to have
specific goals for the desired tuning outcomes.

This document provides tuning information for the following types of I/O:

• Base I/O
• Network
• Storage
• Virtual

Each I/O type is described in an individual tuning section because each I/O type has
unique performance tuning techniques and tunable parameters.

When tuning a system for performance, a performance baseline should first be
measured. Tuning changes should be made incrementally or in small sets. After
changes are made, the performance of the system should be re-measured so that the
effects of the changes can be quantified in relation to the baseline. This will allow you
to identify the most beneficial tunings.

Many factors influence the performance in a system. This document describes some
best practices for performance optimization in Linux on Power systems. Actual
performance measurements may vary.