Skip site navigation (1) Skip section navigation (2)

Re: shared_buffers > 284263 on OS X

From: Dave Cramer <pg(at)fastcrypt(dot)com>
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 16:17:01
Message-ID: 82E59D2F-0946-4405-8F11-4CF5184A9399@fastcrypt.com (view raw or flat)
Thread:
Lists: pgsql-performance
Brian,
On 16-Nov-06, at 7:03 PM, Brian Wipf 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:
>
> FATAL:  could not create shared memory segment: Cannot allocate memory
> DETAIL:  Failed system call was shmget(key=5432001,  
> size=3289776128, 03600).
>
> shmmax and shmall are set to 4GB, as can be seen by the output from  
> sysctl:
> hw.physmem = 2147483648
> hw.usermem = 1885794304
> hw.memsize = 8589934592
> kern.sysv.shmmax: 4294967296
> kern.sysv.shmmin: 1
> kern.sysv.shmmni: 32
> kern.sysv.shmseg: 8
> kern.sysv.shmall: 1048576
>
> 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 ?

Dave
>
> Brian Wipf
> <brian(at)clickspace(dot)com>
>
>
> ---------------------------(end of  
> broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>


In response to

Responses

pgsql-performance by date

Next:From: Guido NeitzerDate: 2006-11-18 17:48:07
Subject: Re: shared_buffers > 284263 on OS X
Previous:From: Joshua MarshDate: 2006-11-18 14:27:09
Subject: Re: start up cost estimate

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group