From: Harald Armin Massa <haraldarminmassa@gmail.com>
To: Magnus Hagander <mha@sollentuna.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: measuring shared memory usage on Windows
Date: Mon, 16 Oct 2006 22:30:27 +0200
Message-ID: <7be3f35d0610161330r4df390f2uecf8d411c861911c@mail.gmail.com> (raw)
In-Reply-To: <6BCB9D8A16AC4241919521715F4D8BCEA357F5@algol.sollentuna.se>
References: <7be3f35d0610160518h649c8f20pee9949a90796c346@mail.gmail.com>
<6BCB9D8A16AC4241919521715F4D8BCEA357F5@algol.sollentuna.se>
Magnus,
> That shows that you don't really know how the memory manager in NT+
> works ;-) *ALL* normal file I/O is handled through the memory manager
> :-) So yes, they are both different access methods to the memory
> manager, really.
"don't really" is a overstatement, I do not know at all how the memory
manager works in NT+. All I learned is "Inside Windows NT" of H.
Custer from 1993 :)
So, just to make sure I understood correctly:
If PostgreSQL reads a file from disk, Windows NT does this file I/O
though the same memory manager than when PostgreSQL puts parts of this
read file [for example an index segment] into shared memory - which is
nothing but a file, that usually stays in main memory.
Correct so far?
I continued from this thoughts:
lets say there is 500MB memory available, we have 100MB of
shared_memory configured.
Now PostgreSQL reads 100MB from a file - memory manager takes 100MB
memory to fullfill this file access (optimizations aside)
Now PostgreSQL reshuffles that 100MB and decides: "hmmmm, that may be
valuable for ALL of the currently running postgres.exe" and pushes
those 100MB into shared memory for all to use. It caches the 100MB - a
fine chunk of an index.
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To: pgsql-performance@postgresql.org
Cc: haraldarminmassa@gmail.com, mha@sollentuna.net
Subject: Re: measuring shared memory usage on Windows
In-Reply-To: <7be3f35d0610161330r4df390f2uecf8d411c861911c@mail.gmail.com>
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