From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: pgsql-performance@postgresql.org
Subject: Re: The right SHMMAX and FILE_MAX
Date: Mon, 02 May 2011 21:06:28 +1200
Message-ID: <4DBE7414.2010902@catalyst.net.nz> (raw)
In-Reply-To: <BANLkTinCr_+Hs_zzHPb+tBdtuLFhrsfKdg@mail.gmail.com>
References: <BANLkTinCr_+Hs_zzHPb+tBdtuLFhrsfKdg@mail.gmail.com>
On 01/05/11 18:48, Phoenix Kiula wrote:
> Now, according to my reading in the PG manual and this list, a good
> recommended value for SHMMAX is
>
> (shared_buffers * 8192)
>
> My postgresql.conf settings at the moment are:
>
> max_connections = 300
> shared_buffers = 300MB
> effective_cache_size = 2000MB
>
> By this calculation, shared_b * 8192 will be:
>
> 2,457,600,000,000
>
> That's a humongous number. So either the principle for SHMMAX is
> amiss, or I am reading this wrongly?
You are confusing shared_buffers expressed as "number of pages" with
shared_buffers expressed as "MB". The docs are assuming you are working
with the former (and would appear to be assuming your pagesize is 8K -
which is teh default but not required to be the case). If you are
showing shared_buffers as "MB" then obviously you cane set SHMMAX using
the value multiplied by (1024*1024), so in your case:
300 * (1024*1024) = 314572800
However note that there are things other than shared_buffers require
shared memory, so you'll need more than this. Use Greg's script.
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: mark.kirkwood@catalyst.net.nz
Subject: Re: The right SHMMAX and FILE_MAX
In-Reply-To: <4DBE7414.2010902@catalyst.net.nz>
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