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https://issues.apache.org/jira/browse/HADOOP-13782?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Zhe Zhang updated HADOOP-13782:
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    Target Version/s: 2.7.4

> Make MutableRates metrics thread-local write, aggregate-on-read
> ---------------------------------------------------------------
>
>                 Key: HADOOP-13782
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13782
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: metrics
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>         Attachments: HADOOP-13782.000.patch, HADOOP-13782.001.patch, 
> HADOOP-13782.002.patch, HADOOP-13782.003.patch, HADOOP-13782.004.patch
>
>
> Currently the {{MutableRates}} metrics class serializes all writes to metrics 
> it contains because of its use of {{MetricsRegistry.add()}} (i.e., even two 
> increments of unrelated metrics contained within the same {{MutableRates}} 
> object will serialize w.r.t. each other). This class is used by 
> {{RpcDetailedMetrics}}, which may have many hundreds of threads contending to 
> modify these metrics. Instead we should allow updates to unrelated metrics 
> objects to happen concurrently. To do so we can let each thread locally 
> collect metrics, and on a {{snapshot}}, aggregate the metrics from all of the 
> threads. 
> I have collected some benchmark performance numbers in HADOOP-13747 
> (https://issues.apache.org/jira/secure/attachment/12835043/benchmark_results) 
> which indicate that this can bring significantly higher performance in high 
> contention situations. 



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