Re: [PATCH] Use MAP_HUGETLB where supported (v3)

On Thu, Oct 24, 2013 at 9:06 AM, Heikki Linnakangas
<hlinnakangas(at)vmware(dot)com> wrote:
> * the documentation should perhaps mention that the setting only has an
> effect if POSIX shared memory is used. That's the default on Linux, but we
> will try to fall back to SystemV shared memory if it fails.

This is true for dynamic shared memory, but not for the main shared
memory segment. The main shared memory segment is always the
combination of a small, fixed-size System V shared memory chunk and a
anonymous shared memory region created by mmap(NULL, ..., MAP_SHARED).
POSIX shared memory is not used.

(Exceptions: Anonymous shared memory isn't used on Windows, which has
its own mechanism, or when compiling with EXEC_BACKEND, when the whole
chunk is allocated as System V shared memory.)

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company