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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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Erik Krogen updated HADOOP-13782:
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Attachment: HADOOP-13782.000.patch
Attaching v000 patch.
We have decided to create a new class, {{MutableRatesWithAggregation}}, rather
than modify the existing {{MutableRates}} metrics class since it is an
{{Evolving}} interface which can only be changed at a minor version bump, to be
able to backport to older versions. I have aded a comment on {{MutableRates}}
noting that its performance in high contention situations will be lacking in
comparison.
I have updated {{RpcDetailedMetrics}}, the only consumer of {{MutableRates}},
to use {{MutableRatesWithAggregation}} instead since it is a point of
potentially very high contention.
> 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
>
>
> 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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