Based on the rather limited profiling there does not seem to be any major differences between MaxScale 2.3 and 2.3. However, there are a few issues that could be investigated further:

• clock_gettime is called a sufficient number of times so that the time it takes actually is visible in the profiling results. Most of the calles is related to load and statistics calculation, so it should perhaps be something that can be turned on/off.
• MaxScale always sniffs for set sql_mode=[default |oracle] and for the setting of variables related to client directed caching. Both of those could be optional.