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Re: Load distributed checkpoint V3

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: pgsql-patches(at)postgresql(dot)org
Subject: Re: Load distributed checkpoint V3
Date: 2007-03-26 03:13:56
Message-ID: Pine.GSO.4.64.0703252231120.23221@westnet.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
On Mon, 26 Mar 2007, ITAGAKI Takahiro wrote:

> I'm assuming checkpoints are triggered by timeout in normal use -- and 
> it's my recommended configuration whether the patch is installed or not.

I'm curious what other people running fairly serious hardware do in this 
area for write-heavy loads, whether it's timeout or segment limits that 
normally trigger their checkpoints.

I'm testing on a slightly different class of machine than your sample 
results, something that is in the 1500 TPS range running the pgbench test 
you describe.  Running that test, I always hit the checkpoint_segments 
wall well before any reasonable timeout.  With 64 segments, I get a 
checkpoint every two minutes or so.

There's something I'm working on this week that may help out other people 
trying to test your patch out.  I've put together some simple scripts that 
graph (patched) pgbench results, which make it very easy to see what 
changes when you alter the checkpoint behavior.  Edges are still rough but 
the scripts work for me, will be polishing and testing over the next few 
days:

http://www.westnet.com/~gsmith/content/postgresql/pgbench.htm

(Note that the example graphs there aren't from the production system I 
mentioned above, they're from my server at home, which is similar to the 
system your results came from).

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD

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