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Re: hyperthreaded cpu still an issue in 8.4?

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Dave Youatt <dave(at)meteorsolutions(dot)com>
Cc: Greg Smith <gsmith(at)gregsmith(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: hyperthreaded cpu still an issue in 8.4?
Date: 2009-07-28 20:58:51
Message-ID: b42b73150907281358w2feacbbh5a3de12a6e13a7b4@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, Jul 27, 2009 at 2:05 PM, Dave Youatt<dave(at)meteorsolutions(dot)com> wrote:
> On 01/-10/-28163 11:59 AM, Greg Smith wrote:
>> On Tue, 21 Jul 2009, Doug Hunley wrote:
>>
>>> Just wondering is the issue referenced in
>>> http://archives.postgresql.org/pgsql-performance/2005-11/msg00415.php
>>> is still present in 8.4 or if some tunable (or other) made the use of
>>> hyperthreading a non-issue. We're looking to upgrade our servers soon
>>> for performance reasons and am trying to determine if more cpus (no
>>> HT) or less cpus (with HT) are the way to go.
>>
>> If you're talking about the hyperthreading in the latest Intel Nehalem
>> processors, I've been seeing great PostgreSQL performance from those.
>> The kind of weird behavior the old generation hyperthreading designs
>> had seems gone.  You can see at
>> http://archives.postgresql.org/message-id/alpine.GSO.2.01.0907222158050.16713@westnet.com
>> that I've cleared 90K TPS on a 16 core system (2 quad-core
>> hyperthreaded processors) running a small test using lots of parallel
>> SELECTs.  That would not be possible if there were HT spinlock
>> problems still around. There have been both PostgreSQL scaling
>> improvments and hardware improvements since the 2005 messages you saw
>> there that have combined to clear up the issues there.  While true
>> cores would still be better if everything else were equal, it rarely
>> is, and I wouldn't hestitate to jump on Intel's bandwagon right now.
>
> Greg, those are compelling numbers for the new Nehalem processors.
> Great news for postgresql.  Do you think it's due to the new internal
> interconnect, that bears a strong resemblance to AMD's hypertransport
[snip]

as a point of reference, here are some numbers on a quad core system
(2xintel 5160) using the old pgbench, scaling factor 10:

pgbench -S -c 16 -t 10000
starting vacuum...end.
transaction type: SELECT only
scaling factor: 10
query mode: simple
number of clients: 16
number of transactions per client: 10000
number of transactions actually processed: 160000/160000
tps = 24088.807000 (including connections establishing)
tps = 24201.820189 (excluding connections establishing)

This shows actually my system (pre-Nehalem) is pretty close clock for
clock, albeit thats not completely fair..I'm using only 4 cores on
dual core procs.  Still, these are almost two years old now.

EDIT: I see now that Greg has only 8 core system not counting
hyperthreading...so I'm getting absolutely spanked!  Go Intel!

Also, I'm absolutely dying to see some numbers on the high end
W5580...if anybody has one, please post!

merlin

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Subject: Re: hyperthreaded cpu still an issue in 8.4?
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