AMA from Microsoft JDConf

Moderator: Bruno @brunoborges

Panel: George (@gdams_), Kirk (@kcpeppe), Bernhard (@lewurm), Monica (@mon_beck), @Charlie (@crgracie), Martijn (@karianna), Scott (@coolcsh)

This felt more like a panel than an AMA to be because (as far as I can tell), the questions all came from the moderator rather than the audience.

Note: If any of the panelists read this, these are my notes, not a transcript 🙂

  • What would you bring from Java to .NET?
    • Scott: can configure settings for performance. Bruno did something impressive “turning dials” to tune a benchmark and make a huge difference.
  • How tune JVM?
    • Monica: JVM provides a lot of logs. ex: GC log over time shows patterns
  • What about JFR (Java flight recorder) events?
    • Martijn: Used to be commercial, now open source. In built telemetry.
  • ARM
    • Monica: COGS = cost of goods sold. More scaling across threads now.
    • Bernhard: Using ARM64 for 4 years. Before that, mobile phones.
    • Charlie: Not easy to do Java on hardware. Opportunities for less objects on heap. Don’t need to have chip do it for us.
    • Monica; Stack allocation is all about allocating into registers. ARM has more registers available
    • Kirk: Profilers don’t see so even sluggishness.
    • Monica: Some optimizations on memory channels. Buffer size matters.
    • Scott: ARM has Linux support
    • Scott: .NET can allocate memory inside a function on stack (instead of heap). Lets you micro-optimize
    • All: Both .NET and Java have “Unsafe” feature. Smalltalk too [good to know such things develop independently!]
  • OpenJDK
    • George: Java 11 getting more downloads than Java 8. 200 million downloads last week (across all versions)
    • All: New name of AdoptOpenJDK is Eclipse Adoptium. Can never win on creating a good name
    • Scott: Name has to be valid in many countries
  • How is it being a Java developer at Microsoft?
    • Martijn: Leads Java Engineering group. Have a lot of JVM engineers so a lot of C/assembly/yaml.
    • Bernhard: Came from MS .NET team. Can’t write either language, but ARM!
    • Charlie: Worked on J9 until last year. Different JVM, but same things. Good to see another large company in OpenJDK community
    • Kirk: Hope is that more will be built-into JDK and less will require parameters. Will still need some flag because of different needs
    • Monica: JDK background, new to working with .NET team. Similarities across both because managed runtime.
    • Bernhard: JIT (just in time) is more advanced in Java than .NET.
    • George: Benefit from JDKs together. Don’t need to build same thing over and over.
  • Closing
    • All: A lot to learn across language communities

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