To reproduce the issue:

1. run Magnolia bundle (6.1.3) . on Java 8 to publish assets (a few Gigabytes) . --> worked fine
2. run the same bundle as above on Java 11 and it takes so long (hours) for publishing big size images

Notes from customer:

In our production system we have a critical issue. Currently, we have uploaded app images with a total size of ~12GB in assets.

When publishing even a single image, almost every time the instance will utilise the CPU to 100% which cause timeout to all other process (e.g. restful calls from clients) and therefore abnormal functioning of the system.

Workaround
Downgrade (if possible) from Magnolia v6.1.3 to v6.1.2 and images publication works good with Java 11.