Then in Java, if you don't set the limits, it gets the CPU from the VM via Runtime.getRuntime().availableProcessors()... this method returns the number of CPUs of the VM or the value set as CPU Quota. Starting from Java 11 the -XX:+PreferContainerQuotaForCPUCount is by default true. For Java <= 10 the CPU count is equal to the CPU shares. That method then is used to calculate the GC threads, fork join pool size, compiler threads etc. The solution would be to set -XX:ActiveProcessorCount=X where X is ideally the CPU shares value but as we know shares can change over time, so you would change this value over time...

Edit: or set -XX:-PreferContainerQuotaForCPUCount