[jira] [Commented] (KUDU-1712) Schema::EncodeComparableKey burns CPU in compaction

["Todd Lipcon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-1712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15932097#comment-15932097 ] 

Todd Lipcon commented on KUDU-1712:
-----------------------------------

https://gerrit.cloudera.org/#/c/6431/ has an improvement in this area to at least avoid the 'div' instruction, though still caching or codegen is probably preferable.

> Schema::EncodeComparableKey burns CPU in compaction
> ---------------------------------------------------
>
>                 Key: KUDU-1712
>                 URL: https://issues.apache.org/jira/browse/KUDU-1712
>             Project: Kudu
>          Issue Type: Bug
>          Components: perf, tablet
>    Affects Versions: 1.0.1
>            Reporter: Todd Lipcon
>
> Looking at a workload that is CPU-bound in compaction, the top CPU consumer is  kudu::GetKeyEncoder<kudu::faststring>(kudu::TypeInfo const*). This is called for every _cell_ that is part of the compound key, and is quite expensive since it involves a 'div' instruction.
> A very easy win would be to pre-cache the key encoder objects for each of the columns in the schema. A less-easy but probably bigger win would be to codegen the comparable key encoder for the schema.



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