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It's excellent to see that Oracle are letting the JVM development team play. Sun was so resource constrained before the Oracle takeover that it felt like much of the speculative thinking had been pushed to "some time in the future", but looking at the talks in the JVM Language Summit it's clear that Oracle has decided to reverse that so the team are thinking about novel ideas that'll keep the JVM at the forefront of technology. That's good news for all of us!

A note from this newsletter's sponsor

One particular statement caught my notice, John Rose stating that the cache line is going to continue being important for the next 20 years (he couldn't see anything else improving the memory access situation within that period). This reminded me of a talk Brian Goetz gave many years ago about the impact of Moore's law. Brian pointed out that while CPUs (if you include multi-core capability) were continuing along the Moore's law path, memory and comms were both increasing at a much much slower rate. Not an original observation, but Brian continued to point out the clear implication for JVMs: memory access was going to become the bottleneck in CPU processing. Hence the increasing importance of CPU cache lines.

But before you go delving into trying to fit objects in cache lines, be aware that only a tiny percentage of applications currently need this level of tuning, and by the time (if ever) it becomes important for the average JVM application, the JIT compiler will be optimizing code for the CPU caches without you having to do much explicitly.

Now, just before I move on to the usual sections, I have a plea for assistance to relay from the jKool people. They'd like to know what changes their product needs - and will throw in a free t-shirt for that feedback! Finally, on to our usual links to tools, articles, news, talks and as ever, all the extracted tips from all of this month's referenced articles .

News

Java performance tuning related news.

• BIOS settings make a significant difference to how a machine performs
• Oracle produces an experimental (commercial) linux 64bit AOT compiler for JVM 9 (maybe for applications that depserately need to avoid JIT jitter). Options include -XX:+UnlockExperimentalVMOptions -XX:+/-EnableJVMCI -XX:+/-UseJVMCICompiler -XX:+/-TieredCompilation -XX:+/-BootstrapJVMCI -XX:+/-UseAOT -XX:AOTLibrary=XXX.so:YYY.so
• While this is not about Java, it provides a quite generic description of OS level considerations of scaling a server
• Using Fragger and LatencyUtils, Azul's open source tools

Tools

Java performance tuning related tools.

• A fast memory efficient byte array builder
• Facebook using Google FlatBuffers
• Garbage Collection Log Analyzer
• Making recursive methods stack-safe tail recursive

A note from this newsletter's sponsor

Articles

• Lessons learned writing highly available code (Jacob Greenleaf/Imgur Engineering)
• Building Scalable Stateful Services (Caitie McCaffrey/Strange Loop)
• Breaking and entering: lose the lock while embracing concurrency, Part II (Tyler Treat/workiva)
• Elements of Scale: Composing and Scaling Data Platforms (Ben Stopford/benstopford)
• How to load test & tune performance on your API (Part II) (Victor Delgado/3scale)
• Java heap analysis - Out of Memory!!! (Manoj Ramakrishnan/engineeringislife)

Jack Shirazi

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