varnish eats all RAM

Marco Dickert - evolver group marco.dickert at
Thu Apr 29 15:21:04 UTC 2021

Hi all,

we have a weird problem with one of our varnish instances running on debian
buster. The problem is, that varnish consumes all RAM over time and does not
free it again. This leads to service unavailability, until varnish gets either
killed by the oom-killer or restarted via some monitoring service (which we
set up to avoid errors). The system runs on an Intel(R) Xeon(R) CPU
E5335 and has 16GB RAM.

We initially experienced this problem with varnish 6.1 (default debian version),
but we upgraded to varnish 6.6 using the official varnish repos, and this
behaviour persists.

I attached a graph of the RAM usage, in which you can see the continuous
allocation of RAM until the process gets restarted.

Has anyone an idea how we could examine the RAM usage further? 

Used varnish modules:
    - directors
    - std
    - digest
    - cookie

Used varnish options:
    -p listen_depth=4096 \
    -p thread_pool_min=200 \
    -p thread_pool_max=300 \
    -p workspace_backend=64k \
    -p workspace_client=128k \
    -p nuke_limit=1000 \
    -p thread_pools=2 \
    -s malloc,3G

Marco Dickert
Mit freundlichen Grüßen
Marco Dickert

Administration und Technik
evolver services GmbH

Fon	+49 / (0)3 71 / 4 00 03 78 24
Fax	+49 / (0)3 71 / 4 00 03 79

E-Mail	marco.dickert at

Sitz der Gesellschaft:	Chemnitz
Handelsregister:	Amtsgericht Chemnitz, HRB 22649
Geschäftsführer:	Torsten Gramann und Mathias Möckel
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