GemFire 8.0 and 8.1
Total heap value in Pulse is higher than the heap-size claimed by each instance in the cluster
Pulse relies on JMX to get the monitoring data so it doesn't pull data from the OS directly. The total heap is aggregated from the heap size for each member in the cluster.
This aggregation is done with MemberMXBean.maxMemory() which internally uses Runtime rt = Runtime.getRuntime().maxMemory(). The documentation of maxMemory() explains that if no inherent limit is found then it will return java.lang.Long#MAX_VALUE . In the case where no limit has been set in any one of the JVM this will cause the issue.