Re: shared_buffers > 284263 on OS X

Brian Wipf <brian(at)shoptoit(dot)ca> wrote:

> I'm trying to optimize a PostgreSQL 8.1.5 database running on an
> Apple G5 Xserve (dual G5 2.3 GHz w/ 8GB of RAM), running Mac OS X
> 10.4.8 Server.
>
> The queries on the database are mostly reads, and I know a larger
> shared memory allocation will help performance (also by comparing it
> to the performance of the same database running on a SUSE Linux box,
> which has a higher shared_buffers setting).
>
> When I set shared_buffers above 284263 (~ 2.17 GB) in the
> postgresql.conf file, I get the standard error message when trying to
> start the db:

It might be, that you hit an upper limit in Mac OS X:

[galadriel: memtext ] cug $ ./test
test(291) malloc: *** vm_allocate(size=2363490304) failed (error code=3)
test(291) malloc: *** error: can't allocate region
test(291) malloc: *** set a breakpoint in szone_error to debug
max alloc = 2253 M

That seems near the size you found to work.

I don't really know much about that, but it seems you just can't alloc
more memory than a bit over 2GB. So, be careful with my non-existing
knowledge about that ... ;-)

cug