NMT currently mark stack guard pages are committed:

0x00007fc5b47f2000 - 0x00007fc5b48f3000] reserved 1028KB for Thread Stack from
    [0x00007fc60891e467] thread_native_entry(Thread*)+0xe7

        [0x00007fc5b47f2000 - 0x00007fc5b47f6000] committed 16KB from
            [0x00007fc608accb97] StackOverflow::create_stack_guard_pages()+0x57
            [0x00007fc608b8de01] JavaThread::run()+0x31
            [0x00007fc608b913fe] Thread::call_run()+0xde
            [0x00007fc60891e467] thread_native_entry(Thread*)+0xe7

but smaps says otherwise:

7fc5b47f2000-7fc5b47f6000 ---p 00000000 00:00 0
Size: 16 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Rss: 0 kB
Pss: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Anonymous: 0 kB
LazyFree: 0 kB
AnonHugePages: 0 kB
ShmemPmdMapped: 0 kB
FilePmdMapped: 0 kB
Shared_Hugetlb: 0 kB
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
Locked: 0 kB