HugeTLB support (in 8.3)

Solaris port already uses Intimate Shared Memory (ISM) which provides
for huge pages (amongst other things).

Linux also supports HugeTLB, but the linux port doesn't allow this to be
used, as yet. There was a previous objection to supporting this:

http://archives.postgresql.org/pgsql-general/2004-04/msg01176.php

but that restriction has now been removed. When that comment was made we
were still running 7.4 as the main release and it was definitely true at
that time, but many advances have been made since then.

It seems straightforward to allow this as an option when the sysadmin
has preconfigured vm tunables correctly.

This is not appropriate for all cases, but it seems better to allow the
sysadmins to judge those cases for themselves than to prevent any access
to this feature.

Comments?

--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com