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https://issues.apache.org/jira/browse/HBASE-15787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15653345#comment-15653345
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ramkrishna.s.vasudevan commented on HBASE-15787:
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Am not able to add this to RB unless HBASE-15786 is completed I believe. Will
work on adding test cases.
> Change the flush related heuristics to work with offheap size configured
> ------------------------------------------------------------------------
>
> Key: HBASE-15787
> URL: https://issues.apache.org/jira/browse/HBASE-15787
> Project: HBase
> Issue Type: Sub-task
> Components: regionserver
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Fix For: 2.0.0
>
> Attachments: HBASE-15787.patch
>
>
> With offheap MSLAB in place we may have to change the flush related
> heuristics to work with offheap size configured rather than the java heap
> size.
> Since we now have clear seperation of the memstore data size and memstore
> heap size, for offheap memstore
> -> Decide if the global.offheap.memstore.size is breached for blocking
> updates and force flushes.
> -> If the onheap global.memstore.size is breached (due to heap overhead) even
> then block updates and force flushes.
> -> The global.memstore.size.lower.limit is now by default 95% of the
> global.memstore.size. So now we apply this 95% on the
> global.offheap.memstore.size and also on global.memstore.size (as it was done
> for onheap case).
> -> We will have new FlushTypes introduces
> {code}
> ABOVE_ONHEAP_LOWER_MARK, /* happens due to lower mark breach of onheap
> memstore settings
> An offheap memstore can even breach the
> onheap_lower_mark*/
> ABOVE_ONHEAP_HIGHER_MARK,/* happens due to higher mark breach of onheap
> memstore settings
> An offheap memstore can even breach the
> onheap_higher_mark*/
> ABOVE_OFFHEAP_LOWER_MARK,/* happens due to lower mark breach of offheap
> memstore settings*/
> ABOVE_OFFHEAP_HIGHER_MARK;
> {code}
> -> regionServerAccounting does all the accounting.
> -> HeapMemoryTuner is what is litte tricky here. First thing to note is that
> at no point it will try to increase or decrease the
> global.offheap.memstore.size. If there is a heap pressure then it will try to
> increase the memstore heap limit.
> In case of offheap memstore there is always a chance that the heap pressure
> does not increase. In that case we could ideally decrease the heap limit for
> memstore. The current logic of heapmemory tuner is such that things will
> naturally settle down. But on discussion what we thought is let us include
> the flush count that happens due to offheap pressure but give that a lesser
> weightage and thus ensure that the initial decrease on memstore heap limit
> does not happen. Currently that fraction is set as 0.5.
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