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https://issues.apache.org/jira/browse/HDFS-8088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14492997#comment-14492997
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Josh Elser commented on HDFS-8088:
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I re-ran my test on Hadoop-2.7.1-SNAP with your patch applied, Colin, and
things are much happier. The performance is much closer to what I previously
saw with 2.6.0 (without any quantitative measurements). +1 (non-binding, ofc)
Billie pointed me at HDFS-8026 as well. I'll pull that one down and test with
it as DFSOutputStream#writeChunk appeared to be the next, most-painfully traced
method.
> Reduce the number of HTrace spans generated by HDFS reads
> ---------------------------------------------------------
>
> Key: HDFS-8088
> URL: https://issues.apache.org/jira/browse/HDFS-8088
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-8088.001.patch
>
>
> HDFS generates too many trace spans on read right now. Every call to read()
> we make generates its own span, which is not very practical for things like
> HBase or Accumulo that do many such reads as part of a single operation.
> Instead of tracing every call to read(), we should only trace the cases where
> we refill the buffer inside a BlockReader.
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