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Re: [HACKERS] More benchmarking of wal_buffers

From: Neil Conway <neilc(at)samurai(dot)com>
To: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>,pgsql-performance(at)postgresql(dot)org, pgsql-advocacy(at)postgresql(dot)org
Subject: Re: [HACKERS] More benchmarking of wal_buffers
Date: 2003-02-13 06:17:52
Message-ID: 1045117072.16760.7.camel@tokyo (view raw or flat)
Thread:
Lists: pgsql-advocacypgsql-hackerspgsql-performance
On Thu, 2003-02-13 at 00:16, Christopher Kings-Lynne wrote:
> Even if you look at the attached charts and you think that 128 buffers are
> better than 8, think again - there's nothing in it.  Next time I run that
> benchmark it could be the same, lower or higher.  And the difference between
> the worst and best results is less than 3 TPS - ie. nothing.

One could conclude that this a result of the irrelevancy of wal_buffers;
another possible conclusion is that the testing tool (pgbench) is not a
particularly good database benchmark, as it tends to be very difficult
to use it to reproduceable results. Alternatively, it's possible that
the limited set of test-cases you've used doesn't happen to include any
circumstances in which wal_buffers is useful.

We definitely need some better benchmarking tools for PostgreSQL (and
no, OSDB does not cut it, IMHO). I've been thinking of taking a look at
improving this, but I can't promise I'll get the time or inclination to
actually do anything about it :-)

Cheers,

Neil
-- 
Neil Conway <neilc(at)samurai(dot)com> || PGP Key ID: DB3C29FC




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