After upgrading to MongoDB 8.0.8 (from 5.0.14), we started running into this problem with MongoDB consuming too much memory. We also started running it in a Docker container if that makes any difference.

We noticed that this often happens when the balancer is enabled and running.

The memory consumption just grows and only a restart of the process helps.

I'm attaching diagnosting data from one of the instances that experienced this problem.
The memory was growing until the container exited with 137.
It happened at around 6/10/2025 8:00 PM UTC.