D-bus signaling performance

While working on lvm-dubstep the question was posed if D-bus could handle the number of changes that could happen in a short period of time, especially PropertiesChanged signals when a large number of logical volumes or physical volumes were present on the system (eg. 120K PVs and 10K+ LVs).  To test this idea I put together a simple server and client which simply tries to send an arbitrary number of signals as fast as it possibly can.  The number settled upon was 10K because during early testing I was running into time-out exceptions when trying to send more in a row.  Initial testing was done using the dbus-python library and even though numbers seemed sufficient, people asked about sd-bus and sd-bus utilizing kdbus, so the experiment was expanded to include these as well.  Source code for the testing is available here.  

Test configuration

The results:

Messages/second is the total number of messages divided by the total time to receive them.

MiB/Second is the messages per second multiplied by the payload size.

Average time delta is the time difference from when the signal was placed on the bus until is was read by the signal handler.  This shows quite a bit of buffering for the python test case at larger payload sizes.

Percentage of signals that were received by the signal handler.  As you can see once the payload > 2048, kdbus appears to silently discard signals away as nothing appeared in kernel output and the return codes were all good in user space.