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From "stack (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 20:50:47 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15062779#comment-15062779
] 

stack commented on HBASE-14460:
-------------------------------

bq. For branch-1.2, branch-1, and master we can just hold the lock longer in doMiniBatchMutation
and then there's no need for read-uncommitted.

I'd like to do general perf compare first before doing above. Will do in another issue.

I believe I need the READ_UNCOMMITTED in this patch because mvcc is global to the region.
At the end of the increment I add my write to mvcc but other writes that have not yet completed
may hold up my write being 'committed' in mvcc... meantime a new Increment could come in and
not see the just-written value in memstore.

Thanks Elliott.

> [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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