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Date:      Mon, 05 Nov 2012 08:29:13 +0100
From:      Frank Broniewski <brfr@metrico.lu>
To:        freebsd-questions@freebsd.org
Subject:   Re: Why PostgreSQL doesn't start with shared_buffers=6GB ?
Message-ID:  <50976AC9.1010402@metrico.lu>
In-Reply-To: <50970E35.6000600@rawbw.com>
References:  <50970E35.6000600@rawbw.com>

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Hi,

I'm running Postgresql 9.1 on FreeBSD 9.0 with the following settings:

# postgresql.conf
shared_buffers = 8GB # pgtune wizard 2012-04-04

# /boot/loader.conf
kern.ipc.semmni=256
kern.ipc.semmns=512
kern.ipc.semmnu=256
kern.ipc.semumr=200
vm.pmap.shpgperproc=400
vm.pmap.pv_entry_max=50331648

# sysctl -a
kern.ipc.shm_allow_removed: 0
kern.ipc.shm_use_phys: 1
kern.ipc.shmall: 4189816
kern.ipc.shmseg: 128
kern.ipc.shmmni: 192
kern.ipc.shmmin: 1
kern.ipc.shmmax: 17161486336
kern.features.sysv_shm: 1
kern.features.posix_shm: 1


I hope that helps a little bit with value tuning,

Frank


Am 2012-11-05 01:54, schrieb Yuri:
> When I am setting shared_buffers=6GB in postgresql.conf it fails to start:
> DETAIL:  Failed system call was shmget(key=5432001, size=6612361216,
> 03600).
> even though kern.ipc.shmmax is set to ~7GB:
> $ sysctl -a | grep shm
> kern.ipc.shm_allow_removed: 0
> kern.ipc.shm_use_phys: 0
> kern.ipc.shmall: 1310720
> kern.ipc.shmseg: 128
> kern.ipc.shmmni: 192
> kern.ipc.shmmin: 1
> kern.ipc.shmmax: 7000000000
> kern.features.sysv_shm: 1
> kern.features.posix_shm: 1
>
> There are 17GB free memory as reported by top(1).
>
> Why shmget fails despite kern.ipc.shmmax is being high enough?
> Experimentally I found that shared_buffers=5GB also fails but 4GB
> succeeds. Is there another system limit on shmem besides kern.ipc.shmmax ?
>
> 9.1-RC3 and64
>
> Yuri
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-- 
Frank BRONIEWSKI

METRICO s.à r.l.
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L-5433 NIEDERDONVEN

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