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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15950) We are grossly overestimating the memstore size
Date Sat, 04 Jun 2016 01:12:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15315213#comment-15315213
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Andrew Purtell commented on HBASE-15950:
----------------------------------------

bq. Found a very nice library called Java-Object-Layout from OpenJDK. I think we should switch
to using this to estimate the object sizes at runtime.

Nope. JOL is GPL. 

What we can do is periodically run it ourselves to get the estimates for updating the constants
we use to ballpark, and perhaps we can experiment with several different JVMs to come up with
different sets of constants we can switch to given some runtime detection. 

> 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
>            Assignee: 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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