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https://issues.apache.org/jira/browse/HBASE-15787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15682720#comment-15682720
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Anoop Sam John commented on HBASE-15787:
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DefaultHeapMemoryTuner dealing with off heap flush count etc.. IMO we should
avoid this.. Got it why we are doing so.. In case of off heap MSLAB, the
forced flushes might be because of global off heap memstore size pressure or by
global heap memstore overhead. When it is because of the latter, we need to do
some thing in the Heap memory tuner (If possible) Any way we pass this as
blocked flush count. So when we have the flushes because of heap memory
overhead pressure, we account that any way so as to get some help from the
tuner. (possible up)) But when there are no pressure from heap size, and have
lack of space in L1 cache, tuner should down the memstore % and give that space
for L1 cache.. That is ur intent.. I agree to this. And any way we need to
consider flushes because of off heap pressure also.. After all these counts are
used to check whether we have R/W workload and what extend.
May be we can do some sort of math and pass blocked flushes, unblocked flush
with out separation of heap/off heap
Blocked flush = blocked flush by heap overhead pressure + 0.75 * blocked flush
by off heap pressure
Same with unblocked flush count
Why we need on heap off heap diff types in FlushType ?
> 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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