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

Hi Thomas,

I've noticed that your patch adds:

+#if defined(SHM_LGPAGE)
+ /* AIX */
+ shmget_extra_flags = SHM_LGPAGE | SHM_PIN;
+#endif

However, my original patch contained:
| SHM_LGPAGE | SHM_PIN | S_IRUSR | S_IWUSR);

It looks like these 2 additional flags are specific to AIX and, as far as I remember, and based on the man of shmget() of AIX, there are required:
S_IRUSR
Permits the process that owns the data structure to read it.
S_IWUSR
Permits the process that owns the data structure to modify it.
So, I'm adding them to your patch.

I'm now trying to run the tests (some other weird issue during build before broke the whole process).

So, I think that I have to do this change in order to ask SystemV memory mapping on AIX:
--- ./src/bin/pg_upgrade/tmp_check/data/postgresql.conf.ORIGIN
+++ ./src/bin/pg_upgrade/tmp_check/data/postgresql.conf
-#shared_memory_type = mmap # the default is the first option
+shared_memory_type = sysv # the default is the first option

However, I do not master the details of which .conf file is used when testing.

Trying now to rebuild and hope tests will be launched this time.

Regards,

Tony
________________________________
De : Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Envoyé : mardi 10 septembre 2019 00:57
À : Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc : REIX, Tony <tony(dot)reix(at)atos(dot)net>; Andres Freund <andres(at)anarazel(dot)de>; Robert Haas <robertmhaas(at)gmail(dot)com>; Pg Hackers <pgsql-hackers(at)postgresql(dot)org>; EMPEREUR-MOT, SYLVIE <sylvie(dot)empereur-mot(at)atos(dot)net>
Objet : Re: Shared Memory: How to use SYSV rather than MMAP ?

On Wed, Sep 4, 2019 at 10:30 AM Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
> On 2019-Feb-03, Thomas Munro wrote:
> > On Sat, Feb 2, 2019 at 12:49 AM Thomas Munro
> > <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> > > I am planning to commit the 0001 patch shortly, unless there are
> > > objections. I attach a new version, which improves the documentation
> > > a bit (cross-referencing the new GUC and the section on sysctl
> > > settings). That will give us shared_memory_type = sysv.
> >
> > Committed 0001.
>
> So can you please rebase what remains?

Here's a quick rebase. It needs testing, review and (probably)
adjustment from AIX users. I'm not going to be able to do anything
with it on my own due to lack of access, though I'm happy to help get
this committed eventually. If we don't get any traction in this CF,
I'll withdraw this submission for now. For consistency, I think we
should eventually also do the same thing for Linux when using sysv
(it's pretty similar, it just uses different flag names; it may also
be necessary to query the page size and round up the requested size,
on one or both of those OSes; I'm not sure).

--
Thomas Munro
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fenterprisedb.com&amp;data=02%7C01%7Ctony.reix%40atos.net%7C1d6794406e304ea3813b08d7357931e2%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0%7C637036666949593490&amp;sdata=8D7VDNLLLs1Aj9XZ8o%2B3YveH6iDQcM3E67AiE66v4f8%3D&amp;reserved=0

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