Re: Does RelCache/SysCache shrink except when relations are deleted?

From: "MauMau" <maumau307(at)gmail(dot)com>
To: "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>
Cc: "Merlin Moncure" <mmoncure(at)gmail(dot)com>, "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Does RelCache/SysCache shrink except when relations are deleted?
Date: 2011-09-29 13:13:30
Message-ID: 33B435CEAB4146FF83BED284A204FC0B@maumau
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From: "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>
> You don't really know this; some operating systems (Linux in particular)
> does not show shared memory as in use by a process until it is accessed.
> It may very well have well over 1.6 GB of shared_buffers, yet not show
> that in VIRT.

Oh, really? When I started psql just after I set shared_buffers to 2500MB
and ran pg_ctl start, "ps -o vsz -p postgres_PID" showed about 2500MB+some.
ps's vsz is also the amount of virtual memory. But I want to know the
shared_buffers setting.

Anyway, I'd appreciate if anyone could tell me about RelCache/SysCache. As
far as I read the code, PostgreSQL seems to use memory for RelCache/SysCache
without limit until the relations are dropped.

Regards
MauMau

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