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https://issues.apache.org/jira/browse/HBASE-15787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15704459#comment-15704459
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stack commented on HBASE-15787:
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Looking at the patch, can DefaultHeapMemoryTuner be made standalone so it can
be tested in isolation? I'd think getting initial values right would be easy
enough but would be cool if we could run a scenario and watch how the feedback
loop develops over a period of time... see if it settles or if it does a Tacoma
Narrows Bridge behavior.
RegionServerAccounting is memory only? Should it say that it is memory only?
RegionServerMemoryAccounting? Or just MemoryAccounting since the RegionServer
is a given?
This seems pretty important given as we don't have a good way at looking at
offheap:
// TODO : add support for offheap metrics
Why am I doing ABOVE_OFFHEAP_HIGHER_MARK in the HeapMemoryManager (unless
HeapMemoryManager is for both onheap and offheap?)
I gave it a pass.
> 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, HBASE-15787_1.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 introduced
> {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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