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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13876) Improving performance of HeapMemoryManager
Date Mon, 02 Nov 2015 17:50:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14985608#comment-14985608

Elliott Clark commented on HBASE-13876:

The test fixes in here make the memstore tests less flakey ( see also HBASE-14742). I'm going
to pull this into branch-1.2 in order to try and get that branch stable.

> Improving performance of HeapMemoryManager
> ------------------------------------------
>                 Key: HBASE-13876
>                 URL: https://issues.apache.org/jira/browse/HBASE-13876
>             Project: HBase
>          Issue Type: Improvement
>          Components: hbase, regionserver
>    Affects Versions: 2.0.0, 1.0.1, 1.1.0, 1.1.1
>            Reporter: Abhilash
>            Assignee: Abhilash
>            Priority: Minor
>             Fix For: 2.0.0, 1.2.0, 1.3.0
>         Attachments: HBASE-13876-v2.patch, HBASE-13876-v3.patch, HBASE-13876-v4.patch,
HBASE-13876-v5.patch, HBASE-13876-v6.patch, HBASE-13876-v7.patch, HBASE-13876.patch
> I am trying to improve the performance of DefaultHeapMemoryTuner by introducing some
more checks. The current checks under which the DefaultHeapMemoryTuner works are very rare
so I am trying to weaken these checks to improve its performance.
> Check current memstore size and current block cache size. For say if we are using less
than 50% of currently available block cache size  we say block cache is sufficient and same
for memstore. This check will be very effective when server is either load heavy or write
heavy. Earlier version just waited for number of evictions / number of flushes to be zero
which are very rare.
> Otherwise based on percent change in number of cache misses and number of flushes we
increase / decrease memory provided for caching / memstore. After doing so, on next call of
HeapMemoryTuner we verify that last change has indeed decreased number of evictions / flush
either of which it was expected to do. We also check that it does not make the other (evictions
/ flush) increase much. I am doing this analysis by comparing percent change (which is basically
nothing but normalized derivative) of number of evictions and number of flushes during last
two periods. The main motive for doing this was that if we have random reads then we will
be having a lot of cache misses. But even after increasing block cache we wont be able to
decrease number of cache misses and we will revert back and eventually we will not waste memory
on block caches. This will also help us ignore random short term spikes in reads / writes.
I have also tried to take care not to tune memory if do do not have enough hints as unnecessary
tuning my slow down the system.

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