Containers facing OutOfMemory errors running with Generational ZGC

[Luiz Hespanha]

Hello,

First of all, congratulations on the great work with Generational ZGC. We
are having great results.

We run our services using k8s, and a standard setup for the memory of the
containers is to use 85% of the total memory for Java Heap and 15% for the
rest. So, in a service running with 10Gb, 8.5Gb is allocated to the Java
Heap, and 1.5Gb is Off-Heap memory.

When running with G1, 15% of Off-Heap memory is generally enough. But with
Generational ZGC, we see an increase in out-of-memory container errors.
It's not Java Heap Out of Memory, it's out-of-memory in the container. I
started to decrease the ratio between Heap/Off-Heap memory, which was
enough for some cases. However, there are services already running with 45%
of memory allocated Off-Heap and still suffering from errors.

Is it expected that Generational ZGC requires more Off-Heap memory? Our
containers run with around 80Gb of memory each, so for some cases, we are
talking of more than 20Gb allocated Off-Heap in a pod running only the Java
application.

Thanks!

-- 

Confidentiality note: This e-mail may contain confidential information 
from Nu Holdings Ltd and/or its affiliates. If you have received it by 
mistake, please let us know by e-mail reply and delete it from your system; 
you may not copy this message or disclose its contents to anyone; for 
details about what personal information we collect and why, please refer to 
our privacy policy 
<https://api.mziq.com/mzfilemanager/v2/d/59a081d2-0d63-4bb5-b786-4c07ae26bc74/6f4939b9-5f74-a528-1835-596b481dca54>.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/zgc-dev/attachments/20230828/5768b97f/attachment.htm>