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https://issues.apache.org/jira/browse/LOG4J2-1382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15276248#comment-15276248
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Remko Popma commented on LOG4J2-1382:
-------------------------------------
Note that MutableLogEvent.createMemento() also calls getSource() but this is on
purpose (and works this way for Log4jLogEvent as well). So this is not a
problem and should not be changed.
> Performance regression in RewriteAppender
> -----------------------------------------
>
> Key: LOG4J2-1382
> URL: https://issues.apache.org/jira/browse/LOG4J2-1382
> Project: Log4j 2
> Issue Type: Bug
> Components: Appenders
> Affects Versions: 2.6
> Reporter: Remko Popma
> Assignee: Remko Popma
> Fix For: 2.6
>
>
> While working on LOG4J2-1179, I ran into these benchmark results:
> {code}
> Benchmark Mode
> Samples Score Error Units
> o.a.l.l.p.j.Log4j2AppenderComparisonBenchmark.appenderRewrite thrpt
> 5 44263670.008 ± 17389305.070 ops/s
> o.a.l.l.p.j.Log4j2AppenderComparisonBenchmark.end2endRewrite thrpt
> 5 37254.554 ± 16440.919 ops/s
> {code}
> In plain English: directly calling RewriteAppender.append(LogEvent) can do 44
> million ops/sec, but when calling rewriteLogger.debug(msg) to invoke a logger
> that calls this appender, all of a sudden throughput drops to 37 _thousand_
> ops/sec. That's 1000x slower. Fishy...
> Turns out that when rewriting the event we are now including caller location
> information (taking a snapshot of the stack and walking it). Ouch.
> This is a regression caused by the garbage-free stuff. Rewriting the event
> makes a copy of the event and avoids calling LogEvent.getSource() only if the
> event is an instance of Log4jLogEvent, but now we are passing in
> MutableLogEvent.
> The fix is to update Log4jLogEvent.Builder to also avoid calling getSource
> when copying from a MutableLogEvent.
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