Possible memory leak in NDB-API applications?

A customer has recently experienced a possible memory leak in its NDB-API application. What he did was something like:

# ps aux | grep <pid>

over time and then he saw the RSS increasing. When he would have had a look a little longer he would have seen that the RSS consumption would increase up to a certain level and then becomes stable. Which is the expected behaviour.http://www.fromdual.com/possible-memory-leak-in-ndb-api

But how to explain to the customer that his application, which was in fact not doing anything, consumes more RSS?
With a diff over time on /proc/<pid>/smaps we found that this area was the reason:

b67b7000-b6fca000 rw-p b67b7000 00:00 0 (8 Mbyte)
Size:               8268 kB
Rss:                 148 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:       148 kB
Referenced:          148 kB

But what is this meaning? To find the answer we did a strace on the program and got the following system calls:

...
read(5, "127.0.0.1 localhost\n\n# The follo"..., 4096) = 450
close(5) = 0
munmap(0xb7acb000, 4096) = 0
mmap2(NULL, 2117632, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb69bf000 - 0xB6BC4000 (2068 Mbyte)
mmap2(NULL, 2101248, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb67be000 - 0xb69bf000 (2052 Mbyte)
mmap2(NULL, 32768, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ac4000
mprotect(0xb7ac4000, 4096, PROT_NONE) = 0
clone(child_stack=0xb7acb4b4, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|
      CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_C
...

OK. Somebody is allocating 2 times 2 junks of about 2 Mbyte of memory. But what the hell could this be??? During night I found the solution. It is the SendBufferMemory and ReceiveBufferMemory which I have configured in the config.ini to that size...

When you experience similar behaviour on your processes, maybe this little script can help you to find the problem: mem_tracker.sh (378 byte).

By the way, with an other customer we found some other nice behaviour. But this time it was a mysqld: