[jira] [Commented] (CASSANDRA-15215) VIntCoding should read and write more efficiently

["Aleksandr Sorokoumov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-15215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17468706#comment-17468706 ] 

Aleksandr Sorokoumov commented on CASSANDRA-15215:
--------------------------------------------------

I added [~blambov] as a reviewer as he approved the PR to trunk. [~benedict] is there anything I can do to facilitate the merge?

> VIntCoding should read and write more efficiently
> -------------------------------------------------
>
>                 Key: CASSANDRA-15215
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15215
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Local/Compaction, Local/SSTable
>            Reporter: Benedict Elliott Smith
>            Assignee: Aleksandr Sorokoumov
>            Priority: Normal
>             Fix For: 3.0.x, 3.11.x, 4.x
>
>         Attachments: testWriteRandomLongDOP_final.png, writeUnsignedVInt_megamorphic_BB.png, writeUnsignedVInt_megamorphic_DOP.png
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> Most vints occupy significantly fewer than 8 bytes, and most buffers have >= 8 bytes spare, in which case we can construct the relevant bytes in a register and memcpy them to the correct position.  Since we read and write a lot of vints, this waste is probably measurable, particularly during compaction and flush, and can probably be considered a performance bug.



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