Re: More shared buffers causes lower performances - Mailing list pgsql-performance

From Guillaume Smet
Subject Re: More shared buffers causes lower performances
Date
Msg-id 1d4e0c10712260741w1f141fd6x2f482143d526ad48@mail.gmail.com
Whole thread Raw
In response to Re: More shared buffers causes lower performances  (Simon Riggs <simon@2ndquadrant.com>)
Responses Re: More shared buffers causes lower performances
Re: More shared buffers causes lower performances
Re: More shared buffers causes lower performances
List pgsql-performance
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

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