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From "Jingcheng Du (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14460) [Perf Regression] Merge of MVCC and SequenceId (HBASE-HBASE-8763) slowed Increments, CheckAndPuts, batch operations
Date Thu, 17 Dec 2015 09:54:47 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15061811#comment-15061811
] 

Jingcheng Du commented on HBASE-14460:
--------------------------------------

Good catch, Ram!
The rollback in put is out of row lock, the following increment/checkAndMutate can read the
dirty cell with IsolationLevel.READ_UNCOMMITTED. It seems we have to remove the get.setIsolationLevel(IsolationLevel.READ_UNCOMMITTED)
and have to release the lock in doMiniBatchMutation method after the readPt catchs up?

> [Perf Regression] Merge of MVCC and SequenceId (HBASE-HBASE-8763) slowed Increments,
CheckAndPuts, batch operations
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-14460
>                 URL: https://issues.apache.org/jira/browse/HBASE-14460
>             Project: HBase
>          Issue Type: Bug
>          Components: Performance
>            Reporter: stack
>            Assignee: stack
>            Priority: Critical
>         Attachments: 0.94.test.patch, 0.98.test.patch, 1.0.80.flamegraph-7932.svg, 14460.txt,
98.80.flamegraph-11428.svg, HBASE-14460-discussion.patch, client.test.patch, flamegraph-13120.svg.master.singlecell.svg,
flamegraph-26636.094.100.svg, flamegraph-28066.098.singlecell.svg, flamegraph-28767.098.100.svg,
flamegraph-31647.master.100.svg, flamegraph-9466.094.singlecell.svg, hack.flamegraph-16593.svg,
hack.uncommitted.patch, m.test.patch, region_lock.png, testincrement.094.patch, testincrement.098.patch,
testincrement.master.patch
>
>
> As reported by 鈴木俊裕 up on the mailing list -- see "Performance degradation between
CDH5.3.1(HBase0.98.6) and CDH5.4.5(HBase1.0.0)" -- our unification of sequenceid and MVCC
slows Increments (and other ops) as the mvcc needs to 'catch up' to our current point before
we can read the last Increment value that we need to update.
> We can say that our Increment is just done wrong, we should just be writing Increments
and summing on read, but checkAndPut as well as batching operations have the same issue. Fix.



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