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https://issues.apache.org/jira/browse/LOG4J2-1125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14935316#comment-14935316
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Gary Gregory commented on LOG4J2-1125:
--------------------------------------
Background question: Are Log4j objects that can be stopped like Threads, in the
sense that they cannot/shouldn't be started again? If so, should we make
stopping an object clear our thread locals? Or, do we need a shutdown() in
addition to stop()?
> Reuse StringBuilder to improve performance for PatternLayout
> ------------------------------------------------------------
>
> Key: LOG4J2-1125
> URL: https://issues.apache.org/jira/browse/LOG4J2-1125
> Project: Log4j 2
> Issue Type: Improvement
> Components: Layouts
> Affects Versions: 2.3
> Reporter: Remko Popma
> Assignee: Remko Popma
> Fix For: 2.4
>
>
> As part of the investigation for LOG4J2-930 (PatternLayout performance), I
> found that in PatternLayout.toSerializable(), instead of creating a new
> StringBuilder each time this method is called, caching and reusing a
> ThreadLocal<StringBuilder> makes a huge difference in performance.
> *Before (new StringBuilder instance for each event)*
> {code}
> Benchmark Mode Samples
> Score Error Units
> o.a.l.l.p.j.PatternLayoutComparisonBenchmark.log4j2 sample 125646
> 1413.362 ± 33.806 ns/op
> o.a.l.l.p.j.PatternLayoutComparisonBenchmark.logback sample 128680
> 1383.201 ± 33.076 ns/op
> {code}
> *After (reuse ThreadLocal<StringBuilder>)*
> {code}
> Benchmark Mode Samples
> Score Error Units
> o.a.l.l.p.j.PatternLayoutComparisonBenchmark.log4j2 sample 156816
> 1138.547 ± 20.290 ns/op
> o.a.l.l.p.j.PatternLayoutComparisonBenchmark.logback sample 127978
> 1355.166 ± 19.462 ns/op
> {code}
> org.apache.logging.log4j.PerformanceComparison results indicate this improves
> overall performance:
> *Before (new StringBuilder instance for each event)*
> {code}
> Log4j : 1501
> Logback : 1208
> Log4j 2.0: 1646
> ###############################################
> Log4j : 1487
> Logback : 1165
> Log4j 2.0: 1566
> ###############################################
> Log4j : 1490
> Logback : 1170
> Log4j 2.0: 1485
> ###############################################
> Log4j : 1392
> Logback : 1143
> Log4j 2.0: 1629
> {code}
> *After (reuse ThreadLocal<StringBuilder>)*
> {code}
> Log4j : 1498
> Logback : 1202
> Log4j 2.0: 1213
> ###############################################
> Log4j : 1394
> Logback : 1057
> Log4j 2.0: 1290
> ###############################################
> Log4j : 1240
> Logback : 1109
> Log4j 2.0: 1335
> ###############################################
> Log4j : 1310
> Logback : 1146
> Log4j 2.0: 1210
> {code}
> There are more changes for LOG4J2-930, so I am splitting off this item into a
> separate ticket so I can address it and close it.
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