shmmax tops out at 2G?

Kris Kennaway kris at obsecurity.org
Wed Dec 13 00:45:54 PST 2006


On Wed, Dec 13, 2006 at 12:27:22AM -0800, Michael K. Smith - Adhost wrote:
> Hello Bill:
> 
> -----Original Message-----
> From: owner-freebsd-questions at freebsd.org
> [mailto:owner-freebsd-questions at freebsd.org] On Behalf Of Bill Moran
> Sent: Monday, December 11, 2006 2:15 PM
> To: questions at freebsd.org
> Subject: shmmax tops out at 2G?
> 
> 
> uname -a
> FreeBSD db00.lab00 6.2-BETA3 FreeBSD 6.2-BETA3 #1: Fri Dec  8 09:27:37
> EST 2006     root at db00.lab00:/usr/obj/usr/src/sys/DB-2850-amd64  amd64
> 
> sysctl kern.ipc.shmmax=2200000000
> kern.ipc.shmmax: 2100000000 -> -2094967296
> 
> Looks like an unsigned 32-bit int.  That doesn't seem to scale as well
> as
> would be expected on 64-bit arch.
> 
> Is this a mistake, or intentional?  I'm working with some big memory
> systems, and I sure would like to allocate more than 2G for PostgreSQL
> to use ...
> 
> -- 
> Bill Moran
> Collaborative Fusion Inc.
> 
> ---
> 
> This may be a silly question but, have you compiled a PAE-enabled
> kernel?  If not, check out /sys/i386/conf/PAE.

Yeah, it is ;-)  PAE is a hack for legacy i386 systems which cannot run
in full 64-bit (amd64) mode - it's not relevant to this problem.

Bill's guess is probably right, so someone needs to go over the sysv
ipc code and make it 64-bit capable.

Kris
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