Resident/Shared memory size is showing 3 times the given heap size

[Sundara Mohan M]

Hi,
   We are running our server with ZGC and seeing the resident memory size
is approximately 3 times the given heap size. I am a newbie still trying to
understand basic concepts. Can someone help me understand this better

1. Is this expected?
2. At high level i know ZGC is having multiple view of memory region. Can
you explain how this can happen?
3. Also i see something like this in /proc/<pid>/maps

...
13fff9a00000-13fff9c00000 rw-s 5f8e00000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
13fff9c00000-13fff9e00000 rw-s 5fb000000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
13fff9e00000-13fffa000000 rw-s 603200000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
13fffa000000-13fffa200000 rw-s 612c00000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
13fffa200000-13fffa400000 rw-s 61a800000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
13fffa400000-13fffa600000 rw-s 326000000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
13fffa600000-13fffa800000 rw-s 5d3600000 00:12 1488924473
 /mnt/tmpfs/java_heap.10087 (deleted)
...
Why is this still in deleted state?
4. Trying to get heap dump with following command
 jmap -heap <pid> (tried with same user as well root but it is not printing
heap)
Is there something changed regarding dumping heap with ZGC?

TIA
Sundar