On using JFR Analytics to locate a thread leak on a java application.

In which scratching the surface of hashCode() leads to a speleology trip through the JVM source reaching object layout, biased locking, and surprising performance implications of relying on the default hashCode().

Skija a collection of hand-crafted bindings for the JVM to the Skia library (the one that powers Chrome, Android, Flutter and Xamarin).

Surprisingly common scenarios:

• requiring 1G memory to support a few hundred users
• saving 500K session state per user
• requiring 2M for a text index per simple document
• creating 100K temporary objects per user hit

This covers the basics of memory allocation and garbage collection in Java, the different garbage collectors available in HotSpot and how they can be tuned, and finally some anecdotes from Attila’s experiences at Twitter.