Tim Armstrong created IMPALA-8020:
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Summary: Process memory consumption does not include unused
reservations
Key: IMPALA-8020
URL: https://issues.apache.org/jira/browse/IMPALA-8020
Project: IMPALA
Issue Type: Bug
Components: Backend
Reporter: Tim Armstrong
This is being split out from IMPALA-7446, since it's a somewhat separate issue.
The issue is that the process memory consumption only accounts for system
memory allocated from the buffer pool, not for reservations that have not been
fulfilled yet. Reserved allocations do *not* check the process memory limit
before going through, so it's possible that the same memory could be committed
both to a non-reserved allocation and a reserved allocation.
In practice this seems unlikely to cause any real symptoms - it would require:
* the process to be near its memory limit
* a large amount of unused reservation, not offset by free buffers or clean
pages.
* a quick spike in the amount of reservation used
This *could* result in the process going significantly over its memory limit
before queries start to fail and free memory.
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