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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15102) HeapMemoryTuner can "overtune" memstore size and suddenly drop it into blocking zone
Date Thu, 14 Jan 2016 00:08:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15097328#comment-15097328
] 

Ted Yu commented on HBASE-15102:
--------------------------------

Say the value of step was 10 at line 1.
In the if block, the value of step is adjusted to 7.
This results in block cache getting less memory than the amount taken from memstore.

> HeapMemoryTuner can "overtune" memstore size and suddenly drop it into blocking zone
> ------------------------------------------------------------------------------------
>
>                 Key: HBASE-15102
>                 URL: https://issues.apache.org/jira/browse/HBASE-15102
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 2.0.0, 1.2.0, 1.3.0, 1.2.1
>            Reporter: Ashu Pachauri
>            Assignee: Ashu Pachauri
>            Priority: Critical
>         Attachments: HBASE-15102-V0.patch
>
>
> DefaultHeapMemoryTuner often resets the maximum step size for tuning to 8% of total heap
size. Often, when the size of memstore is to be decreased while tuning, the 8% tuning can
suddenly drop the memstore size below the low water mark of the previous memstore size (which
could potentially be  the used size of the memstore)
> This is problematic because suddenly it blocks all the updates by suddenly causing a
situation where memstore used size is above high water mark. This has a very bad performance
impact on an otherwise fine HBase cluster. 



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