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https://issues.apache.org/jira/browse/HBASE-7868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13580346#comment-13580346
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Elliott Clark commented on HBASE-7868:
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HBASE-6852 is for the cache hit branch. For cache misses (all of the hfile
perf runs have caching off) we still do the full concurrent hashmap lookup.
That part is slow.
We can get some perf by just following what cache hit does (an array of atomic
longs) that are looked up by index. There may still be other things that need
to get faster, or better ways that was just my first thought.
Also it would be nice if we could turn the per cf metrics off for people that
are very perf conscience.
> HFile performance regression between 0.92 and 0.94
> --------------------------------------------------
>
> Key: HBASE-7868
> URL: https://issues.apache.org/jira/browse/HBASE-7868
> Project: HBase
> Issue Type: Bug
> Components: io
> Affects Versions: 0.94.5
> Reporter: Matteo Bertozzi
> Assignee: Matteo Bertozzi
> Fix For: 0.94.6
>
> Attachments: hfileperf-graphs.png
>
>
> By HFilePerformanceEvaluation seems that 0.94 is slower then 0.92
> Looking at the profiler for the Scan path, seems that most of the time,
> compared to 92, is spent in the metrics dictionary lookup. [~eclark] pointed
> out the new per family/block metrics.
> By commenting the metrics call in HFileReaderV2, the performance seems to get
> better, but maybe metrics is not the only problem.
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