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Performance Management Guide

Determining the Kind of Performance Problem Reported

When a performance problem is reported, determining the kind of performance problem often helps the performance analyst to narrow the list of possible culprits.

A Particular Program Runs Slowly

Although this situation might seem trivial, there are still questions to be asked:

Everything Runs Slowly at a Particular Time of Day

Most people have experienced the rush-hour slowdown that occurs because a large number of people in the organization habitually use the system at one or more particular times each day. This phenomenon is not always simply due to a concentration of load. Sometimes it is an indication of an imbalance that is (at present) only a problem when the load is high. Other sources of recurring situations in the system should be considered.

If you find that the problem stems from conflict between foreground activity and long-running, CPU-intensive programs that are, or should be, run in the background, consider using the command schedtune -r -d to give the foreground higher priority. See Tuning the Thread-Priority-Value Calculation.

Everything Runs Slowly at Unpredictable Times

The best tool for this situation is an overload detector, such as the filtd program (a component of PTX). The filtd daemon can be set up to execute shell scripts or collect specific information when a particular condition is detected. You can construct a similar, but more specialized, mechanism using shell scripts containing the vmstat, iostat, netstat, sar, and ps commands.

If the problem is local to a single system in a distributed environment, there is probably a pathological program at work, or perhaps two that intersect randomly.

Everything That an Individual User Runs is Slow

Sometimes a system seems to "single out" an individual.

A Number of LAN-Connected Systems Slow Down Simultaneously

There are some common problems that arise in the transition from independent systems to distributed systems. The problems usually result from the need to get a new configuration running as soon as possible, or from a lack of awareness of the cost of certain functions. In addition to tuning the LAN configuration in terms of maximum transmission units (MTU) and mbufs (see Chapter 9. Monitoring and Tuning Communications I/O Use), look for LAN-specific pathologies or nonoptimal situations that may have evolved through a sequence of individually reasonable decisions.

Everything on a Particular Service or Device Slows Down at Times

If everything that uses a particular device or service slows down at times, refer to the topic that covers that particular device or service:

Make sure you have followed the configuration recommendations in the appropriate subsystem manual and the recommendations in the appropriate "Monitoring and Tuning" chapter of this book.

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