When I check Gateway memory usage in task manager and compare it to [System]Gateway/Performance/Memory Usage(gateway status page), always there is a difference between these two values.
Why there is the difference here?
The memory shown in Ignition is Java’s heap. That is, all of the java objects themselves. That won’t include the memory occupied by the JVM native code, nor the JVM’s own internal structures, nor memory allocated by add-on native interfaces (JNI).
Is it possible to get sum of those value in Ignition by Python?
VM native code + the JVM’s own internal structures + nor memory allocated by add-on native interfaces (JNI)
Not sure. Probably via java.lang.management: