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Re: measuring shared memory usage on Windows

From: "Magnus Hagander" <mha(at)sollentuna(dot)net>
To: "Harald Armin Massa" <haraldarminmassa(at)gmail(dot)com>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: measuring shared memory usage on Windows
Date: 2006-10-16 10:17:28
Message-ID: 6BCB9D8A16AC4241919521715F4D8BCEA357EE@algol.sollentuna.se (view raw or flat)
Thread:
Lists: pgsql-performance
> Hello,
> 
> Shridhar Daithankar and Josh Berkus write on 
> http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html
> 
> shared_memory
> 
> """
> There is one way to decide what is best for you. Set a  high 
> value of this parameter and run the database for  typical 
> usage. Watch usage of shared memory using ipcs  or similar 
> tools. A recommended figure would be between  1.2 to 2 times 
> peak shared memory usage.
> """
> 
> I tried to find a way to do this on windows. Scanning all the 
> lines of perfmon memory options, I could not see anithing 
> like "shared memory usage".
> 
> Googling for "shared memory usage" just drove me to some 
> ancient WRONG information that PostgreSQL is not possible on 
> Windows because of lacking shared memory. (guess that was for 
> Windows 95 or similiar)
> 
> So: has anybody a hint how I can check how much shared_memory 
> is really used by PostgreSQL on Windows, to fine tune this parameter?
> 
> I learned the hard way that just rising it can lead to a hard 
> performance loss :)

Not really sure :) We're talking about anonymous mapped memory, and I
don't think perfmon lets you look at that. However, there is no limit to
it as there often is on Unix - you can map up to whatever the virual RAM
size is (2Gb/3Gb dependingo n what boot flag you use, IIRC). You can
monitor it as a part of the total memory useage on the server, but
there's no way to automatically show the difference between them.

//Magnus

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