Re: dynamic shared memory: wherein I am punished for good intentions

On Thu, Oct 10, 2013 at 11:13 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> Since, as has been previously discussed in this forum on multiple
> occasions [citation needed], the default System V shared memory limits
> are absurdly low on many systems, the dynamic shared memory patch
> defaults to POSIX shared memory, which has often been touted as a
> superior alternative [citation needed].  Unfortunately, the buildfarm
> isn't entirely happy with this decision.  On buildfarm member anole
> (HP-UX B.11.31), allocation of dynamic shared memory fails with a
> "Permission denied" error, and on smew (Debian GNU/Linux 6.0), it
> fails with "Function not implemented", which according to a forum
> post[1] I found probably indicates that /dev/shm doesn't mount a tmpfs
> on that box.
>
> What shall we do about this?  I see a few options.
>
> (1) Define the issue as "not our problem".  IOW, as of now, if you
> want to use PostgreSQL, you've got to either make POSIX shared memory
> work on your machine, or change the GUC that selects the type of
> dynamic shared memory used.
>
> (2) Default to using System V shared memory.  If people want POSIX
> shared memory, let them change the default.

Doesn't #2 negate all advantages of this effort?  Bringing sysv
management back on the table seems like a giant step backwards -- or
am I missing something?

http://www.postgresql.org/docs/9.3/interactive/kernel-resources.html#SYSVIPC

merlin