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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15452) Consider removing checkScanOrder from StoreScanner.next
Date Mon, 14 Mar 2016 17:30:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15193690#comment-15193690

Lars Hofhansl commented on HBASE-15452:

Two runs with patch applied (test from HBASE-15453)
10 runs  mean:1727.2 sigma:45.20353968440967
10 runs  mean:1769.9 sigma:16.53148511174964

Two runs without patch:
10 runs  mean:2194.8 sigma:56.31838065853811
10 runs  mean:2183.0 sigma:31.135189095298585

So this saved about 20% of runtime! Shows again that these code paths are extremely hot and
every instruction we can save in these will be noticed!

> Consider removing checkScanOrder from StoreScanner.next
> -------------------------------------------------------
>                 Key: HBASE-15452
>                 URL: https://issues.apache.org/jira/browse/HBASE-15452
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>         Attachments: 15452-0.98.txt
> In looking why we spent so much time in StoreScanner.next when doing a simple Phoenix
count\(*) query I came across checkScanOrder. Not only is this a function dispatch (that the
JIT would eventually inline), it also requires setting the prevKV member for every Cell encountered.
> Removing that logic a yields measurable end-to-end improvement of 5-20% (in 0.98).
> I will repeat this test on my work machine tomorrow.
> I think we're stable enough to remove that check anyway.

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