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Type: Improvement
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Resolution: Done
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Priority: Major - P3
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Affects Version/s: 3.4.0
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Component/s: Aggregation Framework
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None
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Fully Compatible
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Query 2017-01-23
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0
DocumentSourceCursor batch size was changed from 4MB to 16MB for MongoDB 3.4 as part of a broader effort to unify user request batch size at 16MB under SERVER-21797. This change led to a mongo-perf performance regression for the "Aggregation.skip" which appears as slower memcpy operations under VTune under DocumentSourceCursor::loadBatch and is likely due to the larger batches exceeding L2/L3 caches.
Testing across our aggregation micro-benchmarks shows a 4MB DocumentSourceCursor batch size restores previous performance across affected tests and does not penalize tests that may benefit from the batching behavior.
- related to
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SERVER-27520 Allow unsigned types for MONGO_EXPORT_SERVER_PARAMETER
- Closed