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Re: Large database help

From: xbdelacour(at)yahoo(dot)com
To: pgsql-admin(at)postgresql(dot)org
Subject: Re: Large database help
Date: 2001-04-24 00:32:40
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-admin
By my reading, the machine is definitely swapping, and not writing to a log 
file (unless its writing obscene amounts of data to the log, which 
presumably the default settings won't do).

postmaster -i -D /home/mg/pgsql -B 100

produces almost identical results in terms of performance and disk 
activity. top shows that each child only has 2.2MB shared instead of 12MB.

What other program/means do I have to tell if the machine is swapping? Can 
I get a reading as to the amount of data that is actually in physical 
memory within a process?


At 08:24 PM 4/23/01 -0400, Tom Lane wrote:
>xbdelacour(at)yahoo(dot)com writes:
> > I'm no Unix expert, but this would seem to indicate that shmget is
> > successfully allocating 400385024/1024/1024=381MB of shared memory. I 
> don't
> > know enough about how the postgres parent/child/shmem scheme works to know
> > why this is working yet the children only register 12MB of shared memory
> > under top.
>On most of the systems I've worked on, top does not seem to count shmem
>blocks that a process is attached to in the process' memory usage.  So
>that doesn't prove much one way or the other.
>I am wondering if your version of 'top' fails to count swapped-out shmem
>segments against swap space, or something like that.  That'd be a tad
>weird, but it seems very improbable that your machine is not swapping;
>I just do not believe top's claim that no swapping is happening.
>Anyway, the most direct experiment would be to reduce your -B request to
>100MB or so and see how things change...
>                         regards, tom lane

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