IBM Support

Soft lockups and startup timeouts on large systems with over 1 TB of memory

News


Abstract

Systems with memory over 1 TB might exhibit timeouts at startup (falling into emergency mode) or messages about soft lockups after system startup.

Content

Linux Releases Affected
All Linux releases
 
IBM Systems Affected
All IBM Power Systems with more than 1 TB of memory that run Linux
 
Symptoms
Timeouts at startup, or soft lockups after startup might occur because on systems with 1 TB of memory or more, a larger number of units of memory are present. Counting these units can take longer than built-in timeouts allow.
Workaround

Make sure that your logical memory blocks (LMB) size is set as large as possible (4 GB). This action can eliminate startup timeouts and greatly reduce, if not eliminate, soft lockups that occur after startup. The LMB is the amount of memory that the system uses for basic memory manipulations such as hot-add and hot-remove operations. The system maintains a list of these blocks, and examines the blocks for various operations. By using a larger LMB size, the number of blocks that the system is tracking is less and the processing is faster.

Note: You must restart the system after changing the LMB size.

For more information about LMB sizes, see Power10 LMB Sizes.

Fix Outlook
IBM Bugzilla 211538

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Document Information

Modified date:
03 June 2025

UID

ibm17235372

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