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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 Wed, 23 Sep 2015 18:22:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14904974#comment-14904974
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stack commented on HBASE-14460:
-------------------------------

bq. And hold the locks per row until after the sync. 

Folks did a load of work to avoid our having to wait on sync while the row lock was held...


But that was another time. WAL has changed a bunch since then.

We'll have to check perf.... make sure no significant degradation... Ideally, our group commit
will absorb any extra friction doing an append ... and we won't back up to fill all handlers.

If we could lock across an append and perf was ok, then we could refactor the current crazyness
of append, then memstore, then sync...

HBASE-12751 went into trunk yesterday. Trying to backport it to branch-1 now.

Don't we still do an mvcc transaction inside the row lock... we'll wait till mvcc catches
up after we take the row lock... then we complete it and on the end ... So, before releasing
the row lock, we'd stamp the mvcc as current writes sequenceid... unless it had already gone
beyond us?

> [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: 14460.txt, region_lock.png
>
>
> 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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