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From "Ashu Pachauri (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-15102) HeapMemoryTuner can "overtune" memstore size and suddenly drop it into blocking zone
Date Wed, 13 Jan 2016 23:34:39 GMT

     [ https://issues.apache.org/jira/browse/HBASE-15102?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ashu Pachauri updated HBASE-15102:
----------------------------------
    Attachment: HBASE-15102-V0.patch

V0: Choose a conservative approach while decreasing memstore size by choosing min size in
the middle of high water and low water mark. The reason to choose it in the middle rather
than at the previous low water mark is that if we do so, we will trigger too many flushes
at once (because the low water mark will also move down once we bring down the memstore size).

> 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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