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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11767) [0.94] Unnecessary garbage produced by schema metrics during scanning
Date Sat, 16 Aug 2014 07:39:19 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11767?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14099547#comment-14099547
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Lars Hofhansl commented on HBASE-11767:
---------------------------------------

Verified that String/StringBuilder/Char[] are no longer created per row... Saving a whooping
520MB of garbage in my 20m row scan test.
(With the recommended young gen sizes for HBase - around 256mb - this save two entire young
collections.)


> [0.94] Unnecessary garbage produced by schema metrics during scanning
> ---------------------------------------------------------------------
>
>                 Key: HBASE-11767
>                 URL: https://issues.apache.org/jira/browse/HBASE-11767
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.23
>
>         Attachments: 11767.txt
>
>
> Near the end of StoreScanner.next(...) we find this gem:
> {code}
>     } finally {
>       if (cumulativeMetric > 0 && metric != null) {
>         RegionMetricsStorage.incrNumericMetric(this.metricNamePrefix + metric,
>             cumulativeMetric);
>       }
>     }
> {code}
> So, for each row generated we build up a new metric string, that will be identical for
each invocation of the StoreScanner anyway (a store scanner is valid for at most one region
and one operation).



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