Re: Shared Memory: How to use SYSV rather than MMAP ?

On Wed, Dec 19, 2018 at 4:17 AM REIX, Tony <tony(dot)reix(at)atos(dot)net> wrote:
> Here is the patch we are using now on AIX for enabling SysV shm for AIX, which improves greatly the performance on AIX.
>
> It is compile time.
>
> It seems to me that you'd like this to become a shared_memory_type GUC. Correct? However, I do not know how to do.
>
>
> Even as-is, this patch would greatly improve the performance of PostgreSQL v11.1 in the field on AIX machines. So, we'd like this change to be available for AIX asap.
>
>
> What are the next steps to get this patch accepted? or What are your suggestions for improving it?

Hi Tony,

Since it's not fixing a bug, we wouldn't back-patch that into existing
releases. But I agree that we should do something like this for
PostgreSQL 12, and I think we should make it user configurable.

Here is a quick rebase of Andres's shared_memory_type patch for
master, so that you can put shared_memory_type=sysv in postgresql.conf
to get the old pre-9.3 behaviour (this may also be useful for other
operating systems). Here also is a "blind" patch that makes it
respect huge_pages=try/on on AIX (or at least, I think it does; I
don't have an AIX to try it, it almost certainly needs some
adjustments). Thoughts?

--
Thomas Munro
http://www.enterprisedb.com