Slowdown in deregisterVector

[Marcel Schneider]

Hello OMNET++ experts,

I currently try to use OMNET/INET for simulating a datacenter network,
but hit a performance problem. Currently, I have a fairly small network
of 72 StandardHosts, but several hundred TCP flows per host and
therefore more than 50K TCPSessionApps. I can provide the configuration
if needed.

With this configuration, I see a dramatic slowdown after about 100ms
simulated time: in cmdenv express mode, the simulation starts with
around 400K events/s (on my laptop) but slows down to about 20K
events/s. Configurations with a similar total number of packets but
fewer connections run fast until they finish.

Some quick profiling shows the problem is in
`cIndexedFileOutputVectorManager::deregisterVector`. And indeed,
commenting out the implementations in
`omnetpp-5.0/src/envir/envirbase.cc:1490-1520` cures the problem.

Note that I have turned off vector recording using `**.vector-recording
= false` in omnetpp.ini anyways.

Is there a way to fix this properly?

Also, is it a good idea to use one TCPSessionApp per TCP flow? More
questions on this will follow.

Thanks,

Marcel Schneider

[Michael Kirsche]

Interesting observation, which tool did you use to profile your simulation run?
Any other statistics that you enabled in your omnetpp.ini?