Comment 7 for bug 1642068

And running health-check on snapd shows the same king of arena expansions with mmap:

Memory Change via mmap() and munmap():
  PID mmaps munmaps Change (K) Rate (K/Sec)
 21627 snapd 36 1 87124 1452.06 (growing fast)
 21637 snapd 35 1 86992 1449.86 (growing fast)
 21236 snapd 1 1 65536 1092.26 (growing fast)
 21860 snapd 41 1 38971 649.53 (growing fast)
 21665 snapd 41 1 38971 649.53 (growing fast)
 21598 snapd 41 1 38971 649.53 (growing fast)
 21664 snapd 23 2 19995 333.26 (growing fast)
 21707 snapd 12 1 12138 202.31 (growing moderately fast)
 20838 snapd 3 0 9248 154.13 (growing moderately fast)
 20843 snapd 1 0 8196 136.60 (growing moderately fast)