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https://issues.apache.org/jira/browse/HDFS-8088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14498655#comment-14498655
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Billie Rinaldi commented on HDFS-8088:
--------------------------------------
To add to Josh's data, I ran some tests with and without the HDFS-8026 patch
(both started from a clean Accumulo instance). The patch definitely reduced
the 0ms spans; I saw about 4x improvement. There are still a lot of 0ms spans,
though.
{noformat}
Before HDFS-8026:
tserver:DFSOutputStream#writeChunk={type='HDFS', nonzeroCount=5224,
zeroCount=2564098, numTraces=163, log10SpanLength=[2564098, 5114, 85, 24, 1, 0,
0]}
After HDFS-8026:
tserver:DFSOutputStream#write={type='HDFS', nonzeroCount=15263,
zeroCount=2383993, numTraces=667, log10SpanLength=[2383993, 15037, 172, 52, 2,
0, 0]}
{noformat}
> 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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