Application performance can be measured using many different metrics, including startup time, ramp-up time, footprint, and response time, as well as throughput. At Eclipse OpenJ9, we keep a watchful eye on all of these metrics, making sensible tradeoffs and providing tuning options that allow the virtual machine (VM) to be optimized for different workloads.
OpenJDK 8 with OpenJ9 demonstrates significantly better performance than OpenJDK 8 with HotSpot
Shared classes and Ahead-of-Time (AOT) technologies typically reduce startup time. By using -Xquickstart mode as well, you can reduce startup time by up to 42%.
OpenJ9 is highly optimized for cloud workloads, where minimizing memory footprint is important. Out of the box, the footprint is 66% smaller than HotSpot.
OpenJ9 reaches peak throughput on a single CPU core in 8.5 minutes compared with 30 minutes for Hotspot. Ideal for short-lived VMs running in the cloud.
Memory footprint increases rapidly when load is applied. However, at steady state, OpenJ9 consistently used around 63% less physical memory than HotSpot.
Testing shows similar results for OpenJDK 11; OpenJ9 outperforms HotSpot on startup, ramp up, and footprint
By using shared classes cache and AOT technology, OpenJ9 starts in roughly half the time it takes HotSpot.
After startup, the OpenJ9 footprint is half the size of HotSpot, which makes it ideal for cloud workloads.
OpenJ9 reaches peak throughput much faster than HotSpot making it especially suitable for running short-lived applications.
Consistent with the footprint results after startup, the OpenJ9 footprint remains much smaller than HotSpot when load is applied.