Tim Armstrong created IMPALA-9765:
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Summary: Preaggregations should stop expanding if memory is scarce
Key: IMPALA-9765
URL: https://issues.apache.org/jira/browse/IMPALA-9765
Project: IMPALA
Issue Type: Improvement
Components: Backend
Reporter: Tim Armstrong
Assignee: Tim Armstrong
We've seen several workloads recently where the preaggregations expanded to
consume nearly all of the memory reservation on a host, starving the merge agg.
We should think about runtime mechanisms to reduce the impact of this, e.g.
stop expanding once we are low on memory.
I think we'd need to do this based on reservation_limit_ - child_reservations_
- used_reservation_ on the query mem tracker. Various heuristics are possible.
Even something simple like keeping 10-20% free would be beneficial.
Related: IMPALA-2945 IMPALA-9530 IMPALA-9591
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