https://github.com/dask/distributed/pull/6033

conda list --export

# This file may be used to create an environment using:
# $ conda create --name <env> --file <this file>
# platform: osx-arm64
aiobotocore=2.1.2=pyhd8ed1ab_0
aiohttp=3.8.1=py310he2143c4_0
aioitertools=0.10.0=pyhd8ed1ab_0
aiosignal=1.2.0=pyhd8ed1ab_0
anyio=3.5.0=py310hbe9552e_0
appnope=0.1.2=py310hbe9552e_2
argon2-cffi=21.3.0=pyhd8ed1ab_0
argon2-cffi-bindings=21.2.0=py310he2143c4_1
asttokens=2.0.5=pyhd8ed1ab_0
async-timeout=4.0.2=pyhd8ed1ab_0
asyncssh=2.5.0=pyhd8ed1ab_1
atk-1.0=2.36.0=heb41896_4
attrs=21.4.0=pyhd8ed1ab_0
babel=2.9.1=pyh44b312d_0
backcall=0.2.0=pyh9f0ad1d_0
backports=1.0=py_2
backports.functools_lru_cache=1.6.4=pyhd8ed1ab_0
bcrypt=3.2.0=py310he2143c4_2
beautifulsoup4=4.10.0=pyha770c72_0
bleach=4.1.0=pyhd8ed1ab_0
bokeh=2.4.2=py310hbe9552e_0
botocore=1.23.24=pyhd8ed1ab_0
brotlipy=0.7.0=py310he2143c4_1003
bzip2=1.0.8=h3422bc3_4
c-ares=1.18.1=h3422bc3_0
ca-certificates=2021.10.8=h4653dfc_0
cached-property=1.5.2=hd8ed1ab_1
cached_property=1.5.2=pyha770c72_1
cairo=1.16.0=h933af38_1010
certifi=2021.10.8=py310hbe9552e_2
cffi=1.15.0=py310hf10583b_0
cfgv=3.3.1=pyhd8ed1ab_0
cftime=1.6.0=py310hdaceac9_0
charset-normalizer=2.0.12=pyhd8ed1ab_0
click=8.1.1=py310hbe9552e_0
cloudpickle=2.0.0=pyhd8ed1ab_0
coverage=6.2=py310he2143c4_0
cryptography=36.0.2=py310hf1846ab_0
curl=7.82.0=hb0e6552_0
cytoolz=0.11.2=py310he2143c4_1
dask=2022.3.0+11.g7819dcc7=pypi_0
debugpy=1.5.1=py310h1b49c16_0
decorator=5.1.1=pyhd8ed1ab_0
defusedxml=0.7.1=pyhd8ed1ab_0
distlib=0.3.4=pyhd8ed1ab_0
distributed=2022.3.0=pyhd8ed1ab_0
entrypoints=0.4=pyhd8ed1ab_0
executing=0.8.3=pyhd8ed1ab_0
expat=2.4.8=h6b3803e_0
filelock=3.6.0=pyhd8ed1ab_0
filesystem-spec=0.2.0=py_0
flit-core=3.7.1=pyhd8ed1ab_0
font-ttf-dejavu-sans-mono=2.37=hab24e00_0
font-ttf-inconsolata=3.000=h77eed37_0
font-ttf-source-code-pro=2.038=h77eed37_0
font-ttf-ubuntu=0.83=hab24e00_0
fontconfig=2.13.96=hfb34624_2
fonts-conda-ecosystem=1=0
fonts-conda-forge=1=0
freetype=2.10.4=h17b34a0_1
fribidi=1.0.10=h27ca646_0
frozenlist=1.3.0=py310he2143c4_0
fsspec=2022.2.0=pyhd8ed1ab_0
gdk-pixbuf=2.42.8=hdded42e_0
gettext=0.19.8.1=h049c9fb_1008
giflib=5.2.1=h27ca646_2
graphite2=1.3.13=h9f76cd9_1001
graphviz=3.0.0=hd4d4665_1
gtk2=2.24.33=h57013de_2
gts=0.7.6=h4b6d4d6_2
h5py=3.6.0=nompi_py310hb8bbf05_100
harfbuzz=4.2.0=hc345670_0
hdf4=4.2.15=h0ef36ac_3
hdf5=1.12.1=nompi_hf9525e8_104
heapdict=1.0.1=py_0
icu=69.1=hbdafb3b_0
identify=2.4.12=pyhd8ed1ab_0
idna=3.3=pyhd8ed1ab_0
importlib-metadata=4.11.3=py310hbe9552e_0
importlib_resources=5.6.0=pyhd8ed1ab_0
iniconfig=1.1.1=pyh9f0ad1d_0
ipdb=0.13.9=pyhd8ed1ab_0
ipykernel=6.10.0=py310hc469350_0
ipython=8.2.0=py310hbe9552e_0
ipython_genutils=0.2.0=py_1
ipywidgets=7.7.0=pyhd8ed1ab_0
jbig=2.1=h3422bc3_2003
jedi=0.18.1=py310hbe9552e_0
jinja2=3.1.1=pyhd8ed1ab_0
jmespath=0.10.0=pyh9f0ad1d_0
joblib=1.1.0=pyhd8ed1ab_0
jpeg=9e=h3422bc3_0
json5=0.9.5=pyh9f0ad1d_0
jsonschema=4.4.0=pyhd8ed1ab_0
jupyter_client=7.2.1=pyhd8ed1ab_0
jupyter_core=4.9.2=py310hbe9552e_0
jupyter_server=1.16.0=pyhd8ed1ab_0
jupyterlab=3.3.2=pyhd8ed1ab_0
jupyterlab_pygments=0.1.2=pyh9f0ad1d_0
jupyterlab_server=2.12.0=pyhd8ed1ab_0
jupyterlab_widgets=1.1.0=pyhd8ed1ab_0
krb5=1.19.3=hf9b2bbe_0
lcms2=2.12=had6a04f_0
lerc=3.0=hbdafb3b_0
libblas=3.9.0=13_osxarm64_openblas
libcblas=3.9.0=13_osxarm64_openblas
libcurl=7.82.0=hb0e6552_0
libcxx=13.0.1=h6a5c8ee_0
libdeflate=1.10=h3422bc3_0
libedit=3.1.20191231=hc8eb9b7_2
libev=4.33=h642e427_1
libffi=3.4.2=h3422bc3_5
libgd=2.3.3=ha764fb0_2
libgfortran=5.0.0.dev0=11_0_1_hf114ba7_23
libgfortran5=11.0.1.dev0=hf114ba7_23
libglib=2.70.2=h67e64d8_4
libiconv=1.16=h642e427_0
liblapack=3.9.0=13_osxarm64_openblas
libnetcdf=4.8.1=nompi_h96a3436_101
libnghttp2=1.47.0=he723fca_0
libopenblas=0.3.18=openmp_h5dd58f0_0
libpng=1.6.37=hf7e6567_2
librsvg=2.52.5=h6312b7c_2
libsodium=1.0.18=h27ca646_1
libssh2=1.10.0=hb80f160_2
libtiff=4.3.0=h77dc3b6_3
libtool=2.4.6=hbdafb3b_1008
libwebp=1.2.2=h0d20362_0
libwebp-base=1.2.2=h3422bc3_1
libxcb=1.13=h9b22ae9_1004
libxml2=2.9.12=hedbfbf4_1
libzip=1.8.0=h3887732_1
libzlib=1.2.11=h90dfc92_1014
llvm-openmp=13.0.1=h455960f_1
locket=0.2.0=py_2
lz4-c=1.9.3=hbdafb3b_1
markupsafe=2.1.1=py310hf8d0d8f_0
matplotlib-inline=0.1.3=pyhd8ed1ab_0
mistune=0.8.4=py310he2143c4_1005
msgpack-python=1.0.3=py310hd99b56e_0
multidict=6.0.2=py310he2143c4_0
nbclassic=0.3.7=pyhd8ed1ab_0
nbclient=0.5.13=pyhd8ed1ab_0
nbconvert=6.4.5=pyhd8ed1ab_1
nbconvert-core=6.4.5=pyhd8ed1ab_1
nbconvert-pandoc=6.4.5=pyhd8ed1ab_1
nbformat=5.2.0=pyhd8ed1ab_0
ncurses=6.3=hc470f4d_0
nest-asyncio=1.5.4=pyhd8ed1ab_0
netcdf4=1.5.8=nompi_py310h59c055a_101
nodeenv=1.6.0=pyhd8ed1ab_0
notebook=6.4.10=pyha770c72_0
notebook-shim=0.1.0=pyhd8ed1ab_0
numpy=1.22.3=py310h2e04ed8_0
objgraph=3.5.0=pyh9f0ad1d_0
openjpeg=2.4.0=h062765e_1
openssl=1.1.1n=h90dfc92_0
packaging=21.3=pyhd8ed1ab_0
pandas=1.4.1=py310hdead3df_0
pandoc=2.12=hca03da5_0
pandocfilters=1.5.0=pyhd8ed1ab_0
pango=1.50.6=h9fd36ab_0
paramiko=2.10.3=pyhd8ed1ab_0
parso=0.8.3=pyhd8ed1ab_0
partd=1.2.0=pyhd8ed1ab_0
pcre=8.45=hbdafb3b_0
pexpect=4.8.0=pyh9f0ad1d_2
pickleshare=0.7.5=py_1003
pillow=9.0.1=py310hade9107_2
pip=22.0.4=pyhd8ed1ab_0
pixman=0.40.0=h27ca646_0
platformdirs=2.5.1=pyhd8ed1ab_0
pluggy=1.0.0=py310hbe9552e_2
pre-commit=2.17.0=py310hbe9552e_0
prometheus_client=0.13.1=pyhd8ed1ab_0
prompt-toolkit=3.0.27=pyha770c72_0
psutil=5.9.0=py310he2143c4_0
pthread-stubs=0.4=h27ca646_1001
ptyprocess=0.7.0=pyhd3deb0d_0
pure_eval=0.2.2=pyhd8ed1ab_0
py=1.11.0=pyh6c4a22f_0
pycparser=2.21=pyhd8ed1ab_0
pygments=2.11.2=pyhd8ed1ab_0
pynacl=1.5.0=py310he2143c4_0
pyopenssl=22.0.0=pyhd8ed1ab_0
pyparsing=3.0.7=pyhd8ed1ab_0
pyrsistent=0.18.1=py310he2143c4_0
pysocks=1.7.1=py310hbe9552e_4
pytest=7.1.1=py310hbe9552e_0
pytest-asyncio=0.12.0=pypi_0
pytest-cov=3.0.0=pyhd8ed1ab_0
pytest-faulthandler=2.0.1=py_0
pytest-repeat=0.9.1=pyhd8ed1ab_0
pytest-rerunfailures=10.2=pyhd8ed1ab_0
pytest-timeout=2.1.0=pyhd8ed1ab_0
python=3.10.4=hfc7342c_0_cpython
python-dateutil=2.8.2=pyhd8ed1ab_0
python-graphviz=0.19.1=pyhaef67bd_0
python_abi=3.10=2_cp310
pytz=2022.1=pyhd8ed1ab_0
pyyaml=6.0=py310he2143c4_3
pyzmq=22.3.0=py310h7939bef_1
readline=8.1=hedafd6a_0
requests=2.27.1=pyhd8ed1ab_0
s3fs=2022.2.0=pyhd8ed1ab_1
scikit-learn=1.0.2=py310h5f111c3_0
scipy=1.8.0=py310h6ecf4ae_1
send2trash=1.8.0=pyhd8ed1ab_0
setuptools=61.2.0=py310hbe9552e_3
six=1.16.0=pyh6c4a22f_0
sniffio=1.2.0=py310hbe9552e_2
sortedcollections=2.1.0=pyhd8ed1ab_0
sortedcontainers=2.4.0=pyhd8ed1ab_0
soupsieve=2.3.1=pyhd8ed1ab_0
sqlite=3.37.1=h7e3ccbd_0
stack_data=0.2.0=pyhd8ed1ab_0
tblib=1.7.0=pyhd8ed1ab_0
terminado=0.13.3=py310hbe9552e_0
testpath=0.6.0=pyhd8ed1ab_0
threadpoolctl=3.1.0=pyh8a188c0_0
tk=8.6.12=he1e0b03_0
toml=0.10.2=pyhd8ed1ab_0
tomli=2.0.1=pyhd8ed1ab_0
toolz=0.11.2=pyhd8ed1ab_0
tornado=6.1=py310he2143c4_2
traitlets=5.1.1=pyhd8ed1ab_0
typing-extensions=4.1.1=hd8ed1ab_0
typing_extensions=4.1.1=pyha770c72_0
tzdata=2022a=h191b570_0
ukkonen=1.0.1=py310hd99b56e_1
urllib3=1.26.9=pyhd8ed1ab_0
virtualenv=20.14.0=py310hbe9552e_0
wcwidth=0.2.5=pyh9f0ad1d_2
webencodings=0.5.1=py_1
websocket-client=1.3.2=pyhd8ed1ab_0
wheel=0.37.1=pyhd8ed1ab_0
widgetsnbextension=3.6.0=py310hbe9552e_0
wrapt=1.14.0=py310hf8d0d8f_0
xorg-libxau=1.0.9=h27ca646_0
xorg-libxdmcp=1.1.3=h27ca646_0
xz=5.2.5=h642e427_1
yaml=0.2.5=h3422bc3_2
yarl=1.7.2=py310he2143c4_1
zeromq=4.3.4=hbdafb3b_1
zict=2.2.0.dev2=pypi_0
zipp=3.7.0=pyhd8ed1ab_1
zlib=1.2.11=h90dfc92_1014
zstandard=0.17.0=py310he2143c4_0
zstd=1.5.2=h861e0a7_0

git diff

diff --git a/distributed/tests/test_spill.py b/distributed/tests/test_spill.py
index 6ab59593..cea28fe6 100644
--- a/distributed/tests/test_spill.py
+++ b/distributed/tests/test_spill.py
@@ -336,7 +336,13 @@ def test_weakref_cache(tmpdir, cls, expect_cached, size):
     # by PyMalloc when you descope objects, so a brand new object might end up having
     # the same id as a deleted one
     id_x = x.id
+    import weakref
+    ref = weakref.ref(x)
     del x
+    import objgraph
+    obj = ref()
+    if obj:
+        objgraph.show_backrefs(obj)

     if size < 100:
         buf["y"]