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Re: shared_buffers > 284263 on OS X

From: Guido Neitzer <lists(at)event-s(dot)net>
To: Brian Wipf <brian(at)shoptoit(dot)ca>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: shared_buffers > 284263 on OS X
Date: 2006-11-18 18:44:39
Message-ID: C4A74FD0-5520-45D7-9419-0ED051CFD7BA@event-s.net (view raw or flat)
Thread:
Lists: pgsql-performance
Hi.

I've sent this out once, but I think it didn't make it through the  
mail server ... don't know why. If it is a double post - sorry for it.

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


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