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Message-ID: <7be3f35d0610160418u51e4d256k15ee2a5e4ba9433@mail.gmail.com>
Date: Mon, 16 Oct 2006 13:18:40 +0200
From: "Harald Armin Massa" <haraldarminmassa@gmail.com>
To: "Magnus Hagander" <mha@sollentuna.net>
Subject: Re: measuring shared memory usage on Windows
Cc: pgsql-performance@postgresql.org
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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


--=20
GHUM Harald Massa
persuadere et programmare
Harald Armin Massa
Reinsburgstra=DFe 202b
70197 Stuttgart
0173/9409607
-
Python: the only language with more web frameworks than keywords.

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Magnus,<br><br><div><blockquote class=3D"gmail_quote" style=3D"border-left:=
 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex=
;">&gt; So: has anybody a hint how I can check how much shared_memory<br>&g=
t; is really used by PostgreSQL on Windows, to fine tune this parameter?
<br>&gt;<br>&gt; I learned the hard way that just rising it can lead to a h=
ard<br>&gt; performance loss :)<br><br>Not really sure :) We're talking abo=
ut anonymous mapped memory, and I<br>don't think perfmon lets you look at t=
hat.=20
</blockquote><div><br>thanks for the clarification. However,<br><br>&quot;a=
nonymous mapped memory&quot;&nbsp; site:<a href=3D"http://microsoft.com">mi=
crosoft.com</a><br><br>turns out 0 (zero) results. And even splitting it up=
 there seems to be nearly no information ... is the same thing by any chanc=
e also known by different names?=20
<br><br>&gt; However, there is no limit to it as there often is on Unix - y=
ou can map up to whatever the virtual RAM</div><div>&gt; size is (2Gb/3Gb d=
ependingo n what boot flag you use, IIRC). You can<br>&gt; monitor it as a =
part of the total memory useage on the server, but
<br>&gt; there's no way to automatically show the difference between them.<=
br><br>So the &quot;performance shock&quot; with high shared memory gets ob=
vious: memory mapped files get swapped to disk. I assume that swapping is n=
early transparent for the application, leading to a nice trashing ...
<br><br>I'll keep on searching...<br><br>Harald<br><br></div></div><br>-- <=
br>GHUM Harald Massa<br>persuadere et programmare<br>Harald Armin Massa<br>=
Reinsburgstra=DFe 202b<br>70197 Stuttgart<br>0173/9409607<br>-<br>Python: t=
he only language with more web frameworks than keywords.

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