From: Tomas Vondra <tv@fuzzy.cz>
To: pgsql-performance@postgresql.org
Subject: Re: cpu comparison
Date: Mon, 18 Jul 2011 23:56:40 +0200
Message-ID: <4E24AC18.807@fuzzy.cz> (raw)
In-Reply-To: <20110718201132.GI19928@staff-mud-56-27.rice.edu>
References: <4E248E04.2090506@turnkey.bz>
<20110718201132.GI19928@staff-mud-56-27.rice.edu>
Dne 18.7.2011 22:11, ktm@rice.edu napsal(a):
>> > In my testing I have a 32bit CentOS on the x3450, but a 64bit CentOS
>> > on the E5335. Can this make such a bit difference or should the
>> > perform fairly close to the same speed? Both servers have 8GB of
>> > RAM, and the database I tested with is only 3.7GB.
>> >
>> > I'm a bit surprised as the x3450 has DDR3, while the E5335 has DDR2,
>> > and of course because of the cycle speed difference alone I would
>> > think the X3450 should beat the E5335.
>> >
> Yes, you have basically shown that running two different tests give
> different results -- or that an apple is not an orange. You need to
> only vary 1 variable at a time for it to mean anything.
He just run the same test on two different machines - I'm not sure
what's wrong with it? Sure, it would be nice to compare 32bit to 32bit,
but the OP probably can't do that and wonders if this is the cause. Why
is that comparing apples and oranges?
According to http://www.cpubenchmark.net, the X3450 is about 2x as fast
as E5335 (5,298 vs. 2,575), although this is just a synthetic score.
I'm a bit confused by the E5335 cpuinfo output, because it says "cpu
cores : 1" as I'd expect "4" here.
I do recall hyperthreading generally was not recommended for a DB, not
sure if that changed recently. A quick search revealed this post
http://serverfault.com/questions/219791/hyperthreading-vs-sql-server-postgresql
stating that since Nehalem CPUs (and X3450 is Nehalem) this should not
be a problem anymore. Not sure if it's true, I guess it's worth testing
as it might slow down the X3450 box.
OP: We need more details about the test's has run, without them we're
just guessing. Have you collected some system stats (vmstat, iostat)
during the test?
Tomas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz
Subject: Re: cpu comparison
In-Reply-To: <4E24AC18.807@fuzzy.cz>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox