Description of problem:

I've seen memory leaks in my 389-ds processes, ending in the OOM-killer killing
off my dirsrv processes. This has also been reported by others on the
freeipa-users mailing list an other users of 389-ds.

After discussing with Rich Megginson this could be the work of a too low
default nsslapd-cachememsize. The default  nsslapd-cachememsize is 10MB.
According to the 389-ds tuning guide this value should be set to at least 2 x
the id2entry.db4 file. Even a small IPA installation of 37 users and 52 hosts
has a id2entry.db4 file of 7.2MB. This suggests that the default size is too
small.

Rich M. advised that auto-tuning has proven to be more error prone than useful
in the past, however tuning of the nsslapd-cachememsize parameter should be
done on a per-environment basis.

After speaking to Rich M, I suggest two changes to be taken into consideration.

First, significantly increase the default nsslapd-cachememsize, as the default
seem to be way to low even for small installation.

Second, make the nsslapd-cachememsize parameter tunable through the IPA cli/ui,
with a reference from the documentation that this should be performed as a part
of the post-installation process of an IPA environment.

Perhaps there could even be a suggested size based upon the actual installation
given in the IPA cli/ui?

Opening this request as agreed with richm on IRC.