Memory consumption is bigger in native images

In a Kubernetes environment, when I switched from JVM-hotspot images to native images, all built with Spring Native 0.10.0-SNAPSHOT and Spring-Boot 2.5.0-RC1, I notice that memory consumption of pods is bigger for Native images that HotSpot running images.

I coded a POC in https://github.com/scalastic/hotspot-vs-native where hasher-java and rng-java sub-projects are the apps deployed as HotSpot or Native pods in Kubernetes.

Here the screen capture of Grafana showing RAM consumption https://github.com/scalastic/hotspot-vs-native#switch-to-native-built-app:

1. Graphs line Random Number Generation monitors rng-java app
2. Graphs line Hasher monitors hasher-java app

• At 13:51: Switch is done
• Between 13:51 and 13:56: JVM and Native images co-exist
• At 13:56: Only native images exist and we see memory increasing

Is that normal while everyone praises the frugality of native images ? :)

[sdeleuze]

Memory management behavior is very different between hotspot and native, and native will tend to use all the memory available before triggering a GC, so I am not sure you will have a relevant comparison with that methodology.

It could be tempting to configure memory explicitly (see related native documentation) the same way, but even with that the behavior is very different.

To compare, I would advise the limit the amount of memory on both at container level (with low values like 128M or 256M) and compare performances. That will simulate memory constraints Cloud environment which is what we really care about for native.

Also be aware that we have mostly focused on compatibility these days, but 0.11 will be focused on memory footprint with a significant reduction of the reflection config.

Last point, Java 11 variant is impacted by various footprint bugs so I would advise to use Java 8 for now if you want to measure footprint.

Understand! Thanks for the clarification