Follows from #339 (comment) for better focus of the discussion.

So, as the previous issue started to explore multi-threading on the server for better use of resources, I first run a profiling of the app on debian.

Special build with:
qmake "CONFIG+=nosound headless noupcasename debug" "QMAKE_CXXFLAGS+=-pg" "QMAKE_LFLAGS+=-pg" -config debug Jamulus.pro && make clean && make -j

Then run as below, and connecting a couple of clients for a few seconds:
./jamulus --nogui --server --fastupdate

Once disconnecting the clients I gracefully killed the server
pkill -sigterm jamulus

And finally run gprof, with the results posted below:
gprof ./jamulus > gprof.txt

https://gist.github.com/WolfganP/46094fd993906321f1336494f8a5faed

It would be interesting to see those who observed high cpu usage run test sessions and collect profiling information as well to detect bottlenecks and potential code optimizations, before embarking on multi-threading analysis that may require major rewrites.