"Non-heap memory ..." metrics in visor have nothing to do with offheap memory allocated for data regions. "Non-heap memory" returned by visor it's JVM managed memory regions other then heap used for internal JVM purposes (JIT compiler, etc., see [1]). Memory allocated in offheap by Ignite for data regions (via "unsafe") not included into this metrics. Some data region related metrics in visor were implemented in Ignite 2.4.
[1] https://docs.oracle.com/javase/8/docs/api/java/lang/management/MemoryMXBean.html
