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https://issues.apache.org/jira/browse/HBASE-15950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15313540#comment-15313540
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Enis Soztutar commented on HBASE-15950:
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- Overestimating by ~2x for memstore KV size and CSLM size.
- CSLM Index Nodes occupy nearly half of Nodes, which is also estimated
accordingly in ClassSize.CONCURRENT_SKIPLISTMAP_ENTRY.
- Backing KV bytes, in case MSLAB is used should not count ClassSize aligning.
- These are young gen allocations, so if in tenured space, the ClassSize
aligning might be more, and more in-line with the estimations (to be verified).
> 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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