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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10169) remove the unnecessary synchronized in JvmMetrics class
Date Thu, 19 Dec 2013 16:44:12 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13853023#comment-13853023
] 

Jason Lowe commented on HADOOP-10169:
-------------------------------------

Thanks for updating the patch.  One last nit is that this code:

{code}
  if (gcInfo == null) {
      gcInfo = new MetricsInfo[2];
      ....
      MetricsInfo[] previousGcInfo = gcInfoCache.putIfAbsent(gcName, gcInfo);
      if (previousGcInfo == null) {
        return gcInfo;
      }
      return previousGcInfo;
  }
  return gcInfo;
{code}

can be simplified to the following so there aren't so many return statements to track:

{code}
  if (gcInfo == null) {
      gcInfo = new MetricsInfo[2];
      ....
      MetricsInfo[] previousGcInfo = gcInfoCache.putIfAbsent(gcName, gcInfo);
      if (previousGcInfo != null) {
        gcInfo = previousGcInfo;
      }
  }
  return gcInfo;
{code}

> remove the unnecessary  synchronized in JvmMetrics class
> --------------------------------------------------------
>
>                 Key: HADOOP-10169
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10169
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: metrics
>    Affects Versions: 3.0.0, 2.2.0
>            Reporter: Liang Xie
>            Assignee: Liang Xie
>            Priority: Minor
>         Attachments: HADOOP-10169-v2.txt, HADOOP-10169-v3.txt, HADOOP-10169.txt
>
>
> When i looked into a HBase JvmMetric impl, just found this synchronized seems not essential.



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