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One time when I was being interviewed, I was asked if I had a favourite performance bug. It's using a HashMap concurrently (described very clearly by Paul Tyma) which is probably the most common concurrency bug out there!

I was reminded about this because my previous favourite feature bug ("Your Password Must Be at Least 18770 Characters and Cannot Repeat Any of Your Previous 30689 Passwords" - described here, the original bug has since been removed) has just been superseded by this superb file bug which results in the bizarre outcome of not being able to print on Tuesdays!

It's a fascinating example of how chaotic behaviour is caused by integrations in modern systems and leads me to remind you that if you don't know about chaos testing (which is testing for chaotic behaviour, not testing chaotically), you really should get familiar with it - especially since performance is naturally chaotic.

Now on to all the usual newsletter list of links, tips, tools, news and articles, and as usual I've extracted all the tips into this month's tips page

A note from this newsletter's sponsor

News

Java performance tuning related news

• Load test of a compute intensive application comparing 6 Open JDK Java 11 JVMs (Temurin, IBM J9, Coretto, RedHat, Microsoft, Zulu), showing it is worth trying the different distributions if you need to get the last few percent improvement for your application. Recommended from this particular test were Coretto, RedHat, Microsoft
• Value objects will have equal (or very close to) performance of primitives (in exchange for immutability and loss of identity)
• JDK Mission Control 8.3.0 Released, blog includes a list of the new and noteworthy changes

Tools

Java performance tuning related tools

• Using IBM Thread and Monitor Dump Analyzer for Java (TMDA) to identify a performance issue
• Loader for AsyncProfiler, with a bunch of additional features to make it easier to use
• StackTrace and it's uses (monitoring resources, concurrency, critical threads)

Articles

• The State of OpenTelemetry for Java Developers (Philipp Krenn/Devoxx)
• Profiling Tools for Java (Johannes Bechberger/Karlsruhe JUG)
• Using Shared Memory-Mapped Files in Java (Peter Lawrey/QCon)

Jack Shirazi

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