Re: measuring shared memory usage on Windows - Mailing list pgsql-performance

From Harald Armin Massa
Subject Re: measuring shared memory usage on Windows
Date
Msg-id 7be3f35d0610160418u51e4d256k15ee2a5e4ba9433@mail.gmail.com
Whole thread Raw
In response to Re: measuring shared memory usage on Windows  ("Magnus Hagander" <mha@sollentuna.net>)
Responses Re: measuring shared memory usage on Windows
List pgsql-performance
Magnus,

> 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.

thanks for the clarification. However,

"anonymous mapped memory"  site:microsoft.com

turns out 0 (zero) results. And even splitting it up there seems to be nearly no information ... is the same thing by any chance also known by different names?

> However, there is no limit to it as there often is on Unix - you can map up to whatever the virtual 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.

So the "performance shock" with high shared memory gets obvious: memory mapped files get swapped to disk. I assume that swapping is nearly transparent for the application, leading to a nice trashing ...

I'll keep on searching...

Harald


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