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Re: Free Cache Memory (Linux) and Postgresql

From: "Nikolas Everett" <nik9000(at)gmail(dot)com>
To: "Denis Gasparin" <denis(at)edistar(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-general(at)postgresql(dot)org
Subject: Re: Free Cache Memory (Linux) and Postgresql
Date: 2008-09-30 14:03:26
Message-ID: d4e11e980809300703y214c00b4w3f2da7b753bad459@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-general
If its the OS cache the kernel ought to free the memory when there is
something else worth caching.  Its not a big deal if the cache is full so
long as the system still performs well.

On Tue, Sep 30, 2008 at 9:51 AM, Denis Gasparin <denis(at)edistar(dot)com> wrote:

> Tom Lane ha scritto:
> > Denis Gasparin <denis(at)edistar(dot)com> writes:
> >
> >> I'm evaluating to issue the drop_caches kernel command (echo 3 >
> >> /proc/sys/vm/drop_caches) in order to free unused pagecache, directory
> >> entries and inodes.
> >>
> >
> > Why in the world would you think that's a good idea?
> >
> >                       regards, tom lane
> >
> >
> We see cached memory growing on constant base, even if there are no
> connections to database.
>
> We have some tables that are truncated and reloaded with updated data on
> regular basis (3,4 days).
>
> It seems like postgres or the operating system (linux) is keeping in
> cache that old data even if it has been deleted.
>
> We're searching a way to free that memory without shutting down pgsql.
>
> Thank you for your help,
> Denis
>
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