[jira] [Resolved] (IMPALA-5988) Improve MemPool::TryAllocate() efficiency for small strings

["Tim Armstrong (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-5988?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong resolved IMPALA-5988.
-----------------------------------
       Resolution: Fixed
    Fix Version/s: Impala 2.11.0


  IMPALA-5988: optimise MemPool::TryAllocate()

Testing:
Ran core tests.

Perf:
Experiments using this on top of a WIP Avro patch for IMPALA-5307
showed noticable improvements in CPU efficiency - up to 10%

Change-Id: I088012084fe535a67a3cd1103ced5a02027f961a
Reviewed-on: http://gerrit.cloudera.org:8080/8145
Reviewed-by: Tim Armstrong <ta...@cloudera.com>
Tested-by: Impala Public Jenkins

> Improve MemPool::TryAllocate() efficiency for small strings
> -----------------------------------------------------------
>
>                 Key: IMPALA-5988
>                 URL: https://issues.apache.org/jira/browse/IMPALA-5988
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Tim Armstrong
>            Assignee: Tim Armstrong
>              Labels: perf
>             Fix For: Impala 2.11.0
>
>
> There are some places in the code where we allocate many small strings from MemPool::TryAllocate().  The code is not particularly well optimised for this case. Specifically:
> * We always realign to the default alignment even when alignment isn't required.
> * The fast path through the code could be streamlined.
> I noticed this while working on IMPALA-5307 where I'm adding extra calls to allocate strings per-row.



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