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Has anyone been able to set kern.sysv.shmmax above 4MB at all in latest
OS X? I just spent a while trying what seemed every possible
permutation of setting up /etc/sysctl.conf and editing /etc/rc directly,
and it just fails (symptom: sysctl shows shmmax as -1, and Postgres
cannot start).

Grrr. Apple's been pretty lame about this from day one, but at least
it's been possible to do it one way or another.

(Curiously, it seems you can now change shmall after bootup in 10.4.2,
but that's not much help when you can't change shmmax.)

regards, tom lane

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Tom,

On 8/29/05 5:18 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:

> Has anyone been able to set kern.sysv.shmmax above 4MB at all in latest
> OS X? I just spent a while trying what seemed every possible
> permutation of setting up /etc/sysctl.conf and editing /etc/rc directly,
> and it just fails (symptom: sysctl shows shmmax as -1, and Postgres
> cannot start).
>
> Grrr. Apple's been pretty lame about this from day one, but at least
> it's been possible to do it one way or another.
>
> (Curiously, it seems you can now change shmall after bootup in 10.4.2,
> but that's not much help when you can't change shmmax.)

Yes - it's very strange, I've had the same experience though I finally found
that setting SHMMAX and SHMALL to the same values, namely 268435456, seems
to work out fine.

I don't have a hypothesis as to why that value works though. I suspect that
equal values of all sizes would work, though I stopped trying when I found
this pair and it worked on multiple machines.

- Luke



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Tom Lane wrote:

>Has anyone been able to set kern.sysv.shmmax above 4MB at all in latest
>OS X? I just spent a while trying what seemed every possible
>permutation of setting up /etc/sysctl.conf and editing /etc/rc directly,
>and it just fails (symptom: sysctl shows shmmax as -1, and Postgres
>cannot start).'
>
Is this perhaps one of the artificial limitations that they put in
place to make you buy Apple OSX Server?

Sincerely,

Joshua D. Drake



>
>Grrr. Apple's been pretty lame about this from day one, but at least
>it's been possible to do it one way or another.
>
>(Curiously, it seems you can now change shmall after bootup in 10.4.2,
>but that's not much help when you can't change shmmax.)
>
> regards, tom lane
>
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>
> http://www.postgresql.org/docs/faq
>


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"Luke Lonergan" <llonergan@greenplum.com> writes:
> Yes - it's very strange, I've had the same experience though I finally found
> that setting SHMMAX and SHMALL to the same values, namely 268435456, seems
> to work out fine.

Interesting. I wonder if there's some bit of code that thinks that
SHMALL is measured in bytes (contrary to OSX's general convention
that it's measured in pages).

regards, tom lane

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On Aug 29, 2005, at 8:18 PM, Tom Lane wrote:

> Has anyone been able to set kern.sysv.shmmax above 4MB at all in
> latest
> OS X? I just spent a while trying what seemed every possible
> permutation of setting up /etc/sysctl.conf and editing /etc/rc
> directly,
> and it just fails (symptom: sysctl shows shmmax as -1, and Postgres
> cannot start).
>
yeah, you need to set shmmax and shmall. shmall seems to be measured
in pages.
Here's the settings I've been using:

skittlebrau:/etc root# grep shm rc
# sysctl -w kern.sysv.shmmax=4194305 kern.sysv.shmmin=1
kern.sysv.shmmni=32 kern.sysv.shmseg=8 kern.sysv.shmall=1024
sysctl -w kern.sysv.shmmax=335544320
sysctl -w kern.sysv.shmmin=1
sysctl -w kern.sysv.shmmni=32
sysctl -w kern.sysv.shmseg=16
sysctl -w kern.sysv.shmall=327680

and just to verify:

skittlebrau:/etc root# sysctl -a | grep shm
kern.sysv.shmmax: 335544320
kern.sysv.shmmin: 1
kern.sysv.shmmni: 32
kern.sysv.shmseg: 16
kern.sysv.shmall: 327680

I've been running PG ith 10k shared bufs for a while.

The pain is sometimes /ec/rc gets rewritten

--
Jeff Trout <jeff@jefftrout.com>
http://www.jefftrout.com/
http://www.stuarthamm.net/





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In order to get postgres working in concert with an iSight on a
PowerBook, I had to increase shmmax, and it seemed to work just fine
by editing /etc/rc:

sysctl -w kern.sysv.shmmax=134217728 kern.sysv.shmmin=1
kern.sysv.shmmni=32 kern.sysv.shmseg=8 kern.sysv.shmall=1024

After restarting, I have:

# sysctl -a | grep shm
kern.sysv.shmmax: 134217728
kern.sysv.shmmin: 1
kern.sysv.shmmni: 32
kern.sysv.shmseg: 8
kern.sysv.shmall: 1024

Of course, this still doesn't seem to be enough to let postgres play
nicely with the iSight...

--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC

Strategic Open Source: Open Your i™

http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-469-5150
615-469-5151 (fax)

On Aug 29, 2005, at 7:18 PM, Tom Lane wrote:

> Has anyone been able to set kern.sysv.shmmax above 4MB at all in
> latest
> OS X? I just spent a while trying what seemed every possible
> permutation of setting up /etc/sysctl.conf and editing /etc/rc
> directly,
> and it just fails (symptom: sysctl shows shmmax as -1, and Postgres
> cannot start).
>
> Grrr. Apple's been pretty lame about this from day one, but at least
> it's been possible to do it one way or another.
>
> (Curiously, it seems you can now change shmall after bootup in 10.4.2,
> but that's not much help when you can't change shmmax.)
>
> regards, tom lane

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Tom,

On 8/29/05 6:41 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:

> Interesting. I wonder if there's some bit of code that thinks that
> SHMALL is measured in bytes (contrary to OSX's general convention
> that it's measured in pages).

I don't know, but I agree that the behavior has changed from Panther to
Tiger.

I wish BSD/Apple would go the way of Solaris 10 and be dynamic. This
ipc/shmem limits business has been a plague since its introduction.

- Luke



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"Thomas F. O'Connell" <tfo@sitening.com> writes:
> After restarting, I have:

> # sysctl -a | grep shm
> kern.sysv.shmmax: 134217728
> kern.sysv.shmmin: 1
> kern.sysv.shmmni: 32
> kern.sysv.shmseg: 8
> kern.sysv.shmall: 1024

> Of course, this still doesn't seem to be enough to let postgres play
> nicely with the iSight...

Don't you need to increase shmall too?

Also, which OS X release is this? 10.4 seems to have regressed
compared to 10.3 :-(

regards, tom lane

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On Aug 29, 2005, at 10:37 PM, Tom Lane wrote:

> "Thomas F. O'Connell" <tfo@sitening.com> writes:
>
>> After restarting, I have:
>
>
>> # sysctl -a | grep shm
>> kern.sysv.shmmax: 134217728
>> kern.sysv.shmmin: 1
>> kern.sysv.shmmni: 32
>> kern.sysv.shmseg: 8
>> kern.sysv.shmall: 1024
>
>
>> Of course, this still doesn't seem to be enough to let postgres play
>> nicely with the iSight...
>
> Don't you need to increase shmall too?
>
> Also, which OS X release is this? 10.4 seems to have regressed
> compared to 10.3 :-(
>
> regards, tom lane

This is 10.4.2. Everything worked as advertised. I didn't need to
increase shmall for the settings to stick, but maybe I ought to for
them to work.

--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC

Strategic Open Source: Open Your i™

http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-469-5150
615-469-5151 (fax)


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Jeff - <threshar@torgo.978.org> writes:
> On Aug 29, 2005, at 8:18 PM, Tom Lane wrote:
>> Has anyone been able to set kern.sysv.shmmax above 4MB at all in
>> latest OS X?

> yeah, you need to set shmmax and shmall.

Did that. Set shmall first, shmall second, both together in one sysctl
command; no joy anywhere. Are you trying this on fully up-to-date
Tiger?

regards, tom lane

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