Re: shared_buffers > 284263 on OS X

On 18-Nov-06, at 11:30 AM, Tom Lane wrote:
> Dave Cramer <pg(at)fastcrypt(dot)com> writes:
>> On 16-Nov-06, at 7:03 PM, Brian Wipf wrote:
>>> Has anyone else noticed this limitation on OS X? Any ideas on how I
>>> might get shared_buffers higher than 284263?
>
>> My guess is something else has taken shared memory ahead of you. OS X
>> seems to be somewhat strange in how it deals with shared memory. Try
>> allocating more to shmmax ?
>
> Look in "ipcs -m -a" output to check this theory. (I am glad to see
> that ipcs and ipcrm are finally there in recent OS X releases ---
> awhile
> back they were not, leaving people to fly entirely blind while dealing
> with issues like this :-()

ipcs -m -a
Shared Memory:
T ID KEY MODE OWNER GROUP CREATOR CGROUP
NATTCH SEGSZ CPID LPID ATIME DTIME CTIME
m 196607 5432001 --rw------- postgres postgres postgres
postgres 8 -2100436992 223 223 23:00:07 2:49:44 23:00:07

(I also bumped shmmax and shmall to 6GB with the same shared_buffers
limit.)

It certainly is unfortunate if Guido's right and this is an upper
limit for OS X. The performance benefit of having high shared_buffers
on our mostly read database is remarkable.