[jira] [Created] (HADOOP-15551) Avoid use of Java8 streams in Configuration.addTags

["Todd Lipcon (JIRA)" <ji...@apache.org>]

Todd Lipcon created HADOOP-15551:
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             Summary: Avoid use of Java8 streams in Configuration.addTags
                 Key: HADOOP-15551
                 URL: https://issues.apache.org/jira/browse/HADOOP-15551
             Project: Hadoop Common
          Issue Type: Improvement
          Components: performance
    Affects Versions: 3.2
            Reporter: Todd Lipcon
            Assignee: Todd Lipcon


Configuration.addTags oddly uses Arrays.stream instead of a more conventional mechanism. When profiling a simple program that uses Configuration, I found that addTags was taking tens of millis of CPU to do very little work the first time it's called, accounting for ~8% of total profiler samples in my program.

{code}
[9] 4.52% 253 self: 0.00% 0 java/lang/invoke/MethodHandleNatives.linkCallSite
[9] 3.71% 208 self: 0.00% 0 java/lang/invoke/MethodHandleNatives.linkMethodHandleConstant
{code}

I don't know much about the implementation details of the Streams stuff, but it seems it's probably meant more for cases with very large arrays or somesuch. Switching to a normal Set.addAll() call eliminates this from the profile.



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