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

From: Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>
To: "REIX, Tony" <tony(dot)reix(at)atos(dot)net>
Cc: 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>
Subject: Re: Shared Memory: How to use SYSV rather than MMAP ?
Date: 2018-12-25 23:28:54
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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

Attachment Content-Type Size
0001-Add-shared_memory_type-GUC.patch application/x-patch 9.6 KB
0002-Add-huge-page-support-for-AIX.patch application/octet-stream 4.6 KB

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