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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15950) We are grossly overestimating the memstore size
Date Fri, 03 Jun 2016 04:27:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15313550#comment-15313550
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Enis Soztutar commented on HBASE-15950:
---------------------------------------

This is the estimates with using REFERENCE size as 4 bytes assuming compressed pointers: 
{code}
memstore size=3.4 G
memstore KV size=1.3 G
memstore KV bytes size=915.5 M
memstore CSLM size=1.1 G
{code}
25% more space for memstore does not sound bad. And the numbers are still not close enough.


If instead we use {{-XX:-UseCompressedOops}}, the numbers from profiling comes up as: 
{code}
memstore size=3.4 G
memstore KV size=1.12 G
memstore KV bytes size=860 M
memstore CSLM size=1.12G + 572M
{code}
Still some differences. 

> We are grossly overestimating the memstore size
> -----------------------------------------------
>
>                 Key: HBASE-15950
>                 URL: https://issues.apache.org/jira/browse/HBASE-15950
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Enis Soztutar
>             Fix For: 2.0.0
>
>         Attachments: Screen Shot 2016-06-02 at 8.48.27 PM.png
>
>
> While testing something else, I was loading a region with a lot of data. Writing 30M
cells in 1M rows, with 1 byte values. 
> The memstore size turned out to be estimated as 4.5GB, while with the JFR profiling I
can see that we are using 2.8GB for all the objects in the memstore (KV + KV byte[] + CSLM.Node
+ CSLM.Index). 
> This obviously means that there is room in the write cache that we are not effectively
using. 



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