Question & Answer
Question
What are hot cache lines, false sharing, and how do they impact performance?
Answer
From an IBM i performance standpoint, 'hot' cache lines or false sharing can result in higher CPU utilization and consumption with less throughput.
The following documents explain this scaling issue in detail:
| o | NUMA on Power 7 in IBM i - Jan 2010 : http://public.dhe.ibm.com/services/us/igsc/idoctor/perf/P7_NUMA.pdf |
| o | Optimizing for Cache Geometry, section POWER7 and POWER7+ Optimization and Tuning Guide: http://www.redbooks.ibm.com/redbooks/pdfs/sg248079.pdf] |
| o | Cache Coherency, Considerations in software design for multi-core multiprocessor architectures: |
These traces can be used to determine the source of this scaling issue:
| o | Collection services data: Document 686413 , MustGather: (Collecting/Sending in) Collection Services Performance Data for General System Performance Issues from an active collection |
| o | Cache line traces: Cache Line Documents |
| o | PEX TPROF: Document 645957, MustGather: High CPU |
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Modified date:
17 March 2026
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