Suspected memory leak. Odd behavior when adding overlay to image.

[eysteinn]

When processing multiple VIIRS composites, I've noticed that memory usage (Maximum resident set size) goes up greatly when adding overlay to images. In my case it is almost doubling from 6.8GB to 11.6GB when adding overlay is the only change.
In addition the memory goes up by each composited where overlay is added instead of spiking for certain amount of time which suggests some resources are not released.

My python environment:
aggdraw (1.3.11)
appdirs (1.4.3)
asciitree (0.3.3)
certifi (2020.4.5.1)
chardet (3.0.4)
configobj (5.0.6)
dask (2.14.0)
docutils (0.16)
fasteners (0.15)
h5py (2.10.0)
idna (2.9)
monotonic (1.5)
numcodecs (0.6.4)
numpy (1.18.2)
pandas (1.0.3)
Pillow (7.1.1)
pip (9.0.1)
pkg-resources (0.0.0)
pycoast (1.3.2)
pykdtree (1.3.1)
pyorbital (1.5.0)
pyproj (2.6.0)
pyresample (1.15.0)
pyshp (2.1.0)
pyspectral (0.9.5)
python-dateutil (2.8.1)
python-geotiepoints (1.1.8)
pytz (2019.3)
PyYAML (5.3.1)
rabbitlistener (0.1)
requests (2.23.0)
satpy (0.21.0)
scipy (1.4.1)
setuptools (39.0.1)
six (1.14.0)
toolz (0.10.0)
trollimage (1.12.0)
trollsift (0.3.4)
urllib3 (1.25.8)
xarray (0.15.1)
zarr (2.4.0)

[djhoese]

Can you make an example that requires no input data (creates a numpy random array or something) and shows this memory leak so we can try it?