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Posted to issues-all@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2019/01/03 22:44:00 UTC

[jira] [Assigned] (IMPALA-8020) Process memory consumption does not include unused reservations

     [ https://issues.apache.org/jira/browse/IMPALA-8020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong reassigned IMPALA-8020:
-------------------------------------

    Assignee: Tim Armstrong

> 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
>            Assignee: Tim Armstrong
>            Priority: Major
>              Labels: resource-management
>
> 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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