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https://issues.apache.org/jira/browse/HADOOP-13747?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15665789#comment-15665789
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Erik Krogen commented on HADOOP-13747:
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Since HADOOP-13782 created the new {{MutableRatesWithAggregation}} class, which
provides high throughput for a collection of {{MutableRate}}-style metrics
under contention through the use of thread-local metric collection with
aggregation, {{RpcDetailedMetrics}} and the {{FSNamesystemLock}} metrics
(introduced in HDFS-10872) are no longer affected by this change.
The {{LongAdder}} change proposed here could still be useful in situations
where a single {{MutableRate}} or {{MutableCounter}} is accessed by many
threads, e.g. many of the metrics within {{RpcMetrics}}.
> Use LongAdder for more efficient metrics tracking
> -------------------------------------------------
>
> Key: HADOOP-13747
> URL: https://issues.apache.org/jira/browse/HADOOP-13747
> Project: Hadoop Common
> Issue Type: Improvement
> Components: metrics
> Reporter: Zhe Zhang
> Assignee: Erik Krogen
> Attachments: HADOOP-13747.patch, benchmark_results
>
>
> Currently many metrics, including {{RpcMetrics}} and {{RpcDetailedMetrics}},
> use a synchronized counter to be updated by all handler threads (multiple
> hundreds in large production clusters). As [~andrew.wang] suggested, it'd be
> more efficient to use the [LongAdder |
> http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/LongAdder.java?view=co]
> library which dynamically create intermediate-result variables.
> Assigning to [~xkrogen] who has already done some investigation on this.
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