I measured the following values an hour after the servers started running.
|Output bandwidth (Mbps)||1407||1454|
The output bandwidth shows the both versions carried similar loads. It included the rsync and FTP, but HTTP occupied most of it. The version 2.4.1, however, had the much smaller connections and requests per second then the version 2.2.22. I have not read the source code yet, so I cannot state the reason of this situation. I guess these versions use the different ways of measuring those values. As for the usage of memory and CPU, the version 2.4.1 used more than twice as much as the version 2.2.22.
I set the similar configurations to both versions. There is no difference in the configurations to explain such the difference of the usage. I tested MPM modules in the version 2.4.1 at first, but got a similar result. I could not understand such large usage of resources, so I tested the built-in worker and got the above result. I observed the usage by the event MPM for a short while. It used similar amount of resources. I cannot use the series of the version 2.4 on ftp.jaist.ac.jp until it come to use much small resources.