Controlling Application Memory Consumption

An IBM Redpaper publication

Published 20 March 2006

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IBM Form #: REDP-4108-00
(28 pages)

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Authors: Dino Quintero, Dave Brelsford, Dean Burdick, John Lewars, Bill Tuel, Curt Vinson, Brian Marcinkowski


pSeries® nodes with large memories are often used for applications that expect to use all the available real memory, either for one serial application or in aggregate for the tasks of a parallel MPI job running on the node.

If an application accesses real memory beyond the amount available, AIX® 5L™ provides support for paging out less frequently used pages. However, paging is relatively slow compared to central processing unit (CPU) speeds, and adversely affects the critical performance requirement of these applications. Excessive paging can disrupt efficient application execution.

This paper describes mechanisms to help applications use maximum available real memory while protecting the integrity of the node. We achieve this by reducing the risk of paging by applications that demand more real memory than is available.

Table of contents

Why this paper
Determining available real memory
Memory Management with AIX 5L and WLM with Absolute Real Memory Limits
Predefined WLM classes
Running jobs with LoadLeveler and WLM configured
Summary of steps to configure LoadLeveler
Specifying consumable memory requirements in LoadLeveler
Determining when a LoadLeveler job is killed for exceeding the WLM absolute real memory limit
Resource Monitoring on AIX 5L
Notification of the Real Memory Limit Event
Performance implications
APARs required for AIX 5L Version 5.2 and Version 5.3
What the team will address next after the release of this Redpaper
The team that wrote this Redpaper

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