Re: Buffers and MacOS X - Mailing list pgsql-general

Added to 7.3 documentation. Thanks.

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Jeffrey Bohmer wrote:
> >Tom Lane wrote:
> >> Hunter Hillegas <lists@lastonepicked.com> writes:
> >> > We are installing postgres on a MacOS X Server...
> >> > On our Linux box, we had to muddle with some parameters to be able to
> >> > increase the shared memory and buffers in postgres.
> >> > Does anyone know how to do this in OS X? Or is it required?
> >>
> >> In OS X 10.1, the max shared memory was a hardwired number that couldn't
> >> be changed without recompiling the kernel --- and the standard setting
> >> was none too darn large, either :-(.  I dunno if Apple has improved
> >> matters in 10.2.
> >
> >I was going to point him to the development docs, but I see no mention
> >of OSX shared kernel limit tuning in there at all.  Can someone submit
> >info to beef it up for OSX?
>
>
> Here are instructions for setting shared memory limits on Mac OS X 10.2.
>
> Edit the file:
>
>     /System/Library/StartupItems/SystemTuning/SystemTuning
>
> Near the bottom, you will see these lines:
>
>     sysctl -w kern.sysv.shmmax=4194304
>     sysctl -w kern.sysv.shmmin=1
>     sysctl -w kern.sysv.shmmni=32
>     sysctl -w kern.sysv.shmseg=8
>     sysctl -w kern.sysv.shmall=1024
>
> These parameters are described in this document:
>
>     http://www.postgresql.org/idocs/index.php?kernel-resources.html
>
> OS X is simialar to BSD/OS in the values for each parameter.  For my system, I want PostgreSQL to use 128MB worth of
buffers. I used the calculations provided in the "Reasonable Values" column of the parameters table in the document
above.
>
> So here are my settings (allowing a little extra room):
>
>     sysctl -w kern.sysv.shmmax=167772160    # bytes
>     sysctl -w kern.sysv.shmmin=1
>     sysctl -w kern.sysv.shmmni=32
>     sysctl -w kern.sysv.shmseg=8
>     sysctl -w kern.sysv.shmall=65536        # 4K pages
>
> Now, I can set shared_buffers in postgresql.conf to:
>
>     shared_buffers = 16384    # number of buffers, 8K each
>
> - Jeff
> --
>
> Jeff Bohmer
> VisionLink, Inc.
> _________________________________
> 303.402.0170
> www.visionlink.org
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