From: Pavel Stehule <pavel.stehule@gmail.com>
To: Guillaume Smet <guillaume.smet@gmail.com>
Cc: Simon Riggs <simon@2ndquadrant.com>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Cc: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
Subject: Re: More shared buffers causes lower performances
Date: Wed, 26 Dec 2007 18:12:21 +0100
Message-ID: <162867790712260912p1e00dd75yfaebf6fffe6d2403@mail.gmail.com> (raw)
In-Reply-To: <1d4e0c10712260741w1f141fd6x2f482143d526ad48@mail.gmail.com>
References: <1d4e0c10712251606q6f9503deye3da4b68c51bf5e@mail.gmail.com>
<1198668065.4221.288.camel@ebony.site>
<1d4e0c10712260741w1f141fd6x2f482143d526ad48@mail.gmail.com>
Hello
I tested it and it is true. In my configuration 1GRam, Fedora 8, is
PostgreSQL most fast with 32M shared buffers :(. Diff is about 5% to
256M
Regards
Pavel Stehule
On 26/12/2007, Guillaume Smet <guillaume.smet@gmail.com> wrote:
> On Dec 26, 2007 12:21 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> > bgwriter_lru_maxpages = 0
> >
> > So we can see if the bgwriter has any hand in this?
>
> It doesn't change the behaviour I have.
>
> It's not checkpointing either as using pgbench-tools, I can see that
> tps and latency are quite stable during the entire run. Btw, thanks
> Greg for these nice tools.
>
> I thought it may be some sort of lock contention so I made a few tests
> with -N but I have the same behaviour.
>
> Then I decided to perform read-only tests using -S option (pgbench -S
> -s 100 -c 16 -t 30000 -U postgres bench). And still the same
> behaviour:
> shared_buffers=64MB : 20k tps
> shared_buffers=1024MB : 8k tps
>
> Any other idea?
>
> --
> Guillaume
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>
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To: pgsql-performance@postgresql.org
Cc: pavel.stehule@gmail.com, guillaume.smet@gmail.com, simon@2ndquadrant.com, stefan@kaltenbrunner.cc
Subject: Re: More shared buffers causes lower performances
In-Reply-To: <162867790712260912p1e00dd75yfaebf6fffe6d2403@mail.gmail.com>
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