Good observation. Please run the memory statistics CLI commands to get more hints about the module that might cause it (as per below link). Then please report more details. If you can point to a particular module, you can also open an issue on our tracker.
I'm still investigating the (most likely non-kamailio-related) memory leak of my previous message to the list, there have been no developments so far. I'll update if anything changes.
This concerns a new finding which seems to affect kamailio 5.5.x. I have two kamailio instances receiving the same traffic via round-robin. I upgraded only one of them to 5.5.1 and left the other to 5.4.6 as I feared of any issues arising. I was lucky to do so, because with identical configuration, 5.5.x seems to run out of SHM very quickly. Here are links to graphs produced by our monitoring system:
Old kamailio (no memory leak): https://pasteboard.co/K8fVBiD.png
New kamailio (possible leak): https://pasteboard.co/K8fVS9N.png
The configuration uses mtree, htable, vars and vns extensively. Has anyone come across anything similar? Let me know if I can provide any further information to help disect this. Thanks!