

 Hello, hackers!


 I am running postgresql 7.1 on a SMP Linux box. It runs, but it never pass a 
loadavg of 0.4, no matter how I try to overload the system.

 The same configuration, the same executable, the same test on a non-SMP 
machine gives a loadavg of 19.

 That means that a Xeon SMP box with 1Gb of RAM goes slowlier than a weak 
CPU, with the same postgres, the same configuration, and the same test.

 Anybody knows what is happening? Is there something to do on a SMP machine 
for it to run? I tried with lots of shared memory, and with "commit_delay=0", 
but nothing worked.

 Yours:





Thu, 5 Jul 2001 16:51:35 +0200
=?iso-8859-1?q?V=EDctor=20Romero?= <romero@kde.org>
Pg on SMP half-powered

What is the postgres process doing?  what does iostat show for disk I/O?
from reading this, you are comparing apples->oranges ... are the drives
the same on the non-SMP as the SMP?  amount of RAM?  speed of CPUs?  hard
drive controllers with same amount of cache on them? etc, etc, etc ...

On Thu, 5 Jul 2001, [iso-8859-1] V�ctor Romero wrote:

>
>
>  Hello, hackers!
>
>
>  I am running postgresql 7.1 on a SMP Linux box. It runs, but it never pass a
> loadavg of 0.4, no matter how I try to overload the system.
>
>  The same configuration, the same executable, the same test on a non-SMP
> machine gives a loadavg of 19.
>
>  That means that a Xeon SMP box with 1Gb of RAM goes slowlier than a weak
> CPU, with the same postgres, the same configuration, and the same test.
>
>  Anybody knows what is happening? Is there something to do on a SMP machine
> for it to run? I tried with lots of shared memory, and with "commit_delay=0",
> but nothing worked.
>
>  Yours:
>
>
>
>
>
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>

Marc G. Fournier                   ICQ#7615664               IRC Nick: Scrappy
Systems Administrator @ hub.org
primary: scrappy@hub.org           secondary: scrappy@{freebsd|postgresql}.org


Thu, 5 Jul 2001 14:34:26 -0300 (ADT)
The Hermit Hacker <scrappy@hub.org>
Re: Pg on SMP half-powered
El Jueves 05 Julio 2001 19:34, The Hermit Hacker escribiï¿½:
> What is the postgres process doing?  what does iostat show for disk I/O?
> from reading this, you are comparing apples->oranges ... are the drives
> the same on the non-SMP as the SMP?  amount of RAM?  speed of CPUs?  hard
> drive controllers with same amount of cache on them? etc, etc, etc ...

	The postgres is doing inserts, but it does not matter. Other tests and 
benchs do the same weird results. All the process stay the most of the time 
sleeping.

	The disk of the non-SMP is a cheap IDE. The disk of the SMP is a SCSI-2 
disk. Bonnie and other benchs give to the SMP machine better results (that is 
evident). Thay is what does strange that postgres run fater on the non-SMP 
machine.

	(about comparing apples with oranges) Yes, I know. More exactly, I am 
comparing a F-1 car with a bike, bike run faster, and I ask on the F-1 
experts mailing list why.

 	RAM: 1Gb on the SMP machine. 128Mb on the non-SMP machine.

 	Speed: 400MHz on the non-SMP machine. 550 on the SMP one.

           The SMP machine is far away better than the non-SMP one. Same OS, 
same distro, same Postgres, same test, and a cheap non-SMP machine 
outperforms a very expensive HP SMP server. It looks a interblocking stuff, 
due to all the postmasters are sleeping but one, meanwhile on the non-SMP 
they runs concurently. Does anybody knows what is happening?


 Yours:

 

Fri, 6 Jul 2001 10:52:33 +0200
=?iso-8859-1?q?V=EDctor=20Romero?= <romero@kde.org>
Re: Pg on SMP half-powered
On 06 Jul 2001 10:52:33 +0200, Vï¿½ctor Romero wrote:

>       (about comparing apples with oranges) Yes, I know. More exactly, I am 
> comparing a F-1 car with a bike, bike run faster, and I ask on the F-1 
> experts mailing list why.
> 
>       RAM: 1Gb on the SMP machine. 128Mb on the non-SMP machine.
> 
>       Speed: 400MHz on the non-SMP machine. 550 on the SMP one.
> 
>            The SMP machine is far away better than the non-SMP one. Same OS, 
> same distro, same Postgres, same test, and a cheap non-SMP machine 
> outperforms a very expensive HP SMP server. It looks a interblocking stuff, 
> due to all the postmasters are sleeping but one, meanwhile on the non-SMP 
> they runs concurently. Does anybody knows what is happening?
> 
> 
>  Yours:


What kernel version? 2.4.x has had problems with mtrr on SMP Xeon
systems and we had to upgrade to 2.2.19 to get 2.2.x to use the L2 cache
on newer Xeon CPU's. The default redhat kernel had no idea what they
were, according to our sysadmin here and they ended up running with L2
cahce disabled. And then we ran into problems with bigmem with RedHat's
2.2.19 upgrade and decided that the better route was to complile our own
, ensuring all of your hardware gets explicitly supported properly.


-- 
Colin M Strickland  perl -e'print "\n",map{chr(ord()-3)}(reverse split 
             //,"\015%vhlwlqxpprF#ir#uhzrS#hkw#jqlvvhqudK%#\015\015nx".
"1rf1wilv1zzz22=swwk###369<#84<#:44#77.={di##339<#84<#:44#77.=ohw\015]".
"K9#4VE#/ORWVLUE#/whhuwV#dlurwflY#334#/wilV\015uhsrohyhG#ehZ#urlqhV");'

06 Jul 2001 10:36:38 +0100
Colin Strickland <cms@sift.co.uk>
Re: Pg on SMP half-powered
On Thursday 05 July 2001 10:51, Vï¿½ctor Romero wrote:
>  I am running postgresql 7.1 on a SMP Linux box. It runs, but it never pass
> a loadavg of 0.4, no matter how I try to overload the system.

>  The same configuration, the same executable, the same test on a non-SMP
> machine gives a loadavg of 19.

Sounds like a kernel issue.

However, the load average numbers alone are not enough information to get a 
benchmark.  You need to benchmark using a benchmark that can generate enough 
traffic to load both machines and get good time results for the run of the 
standard benchmark queries.
--
Lamar Owen
WGCR Internet Radio
1 Peter 4:11

Sat, 7 Jul 2001 10:36:29 -0400
Lamar Owen <lamar.owen@wgcr.org>
Re: Pg on SMP half-powered
El Sï¿½bado 07 Julio 2001 16:36, Lamar Owen escribiï¿½:
> On Thursday 05 July 2001 10:51, Vï¿½ctor Romero wrote:
> >  I am running postgresql 7.1 on a SMP Linux box. It runs, but it never
> > pass a loadavg of 0.4, no matter how I try to overload the system.
> >
> >  The same configuration, the same executable, the same test on a non-SMP
> > machine gives a loadavg of 19.
>
> Sounds like a kernel issue.
>
> However, the load average numbers alone are not enough information to get a
> benchmark.  You need to benchmark using a benchmark that can generate
> enough traffic to load both machines and get good time results for the run
> of the standard benchmark queries.

	Now Im at home... as soon as I get office again Ill send you the little script benchs I wrote, I think them genetares enough traffic because if I throw more than 400 threads the postmaster start to fail... 

	

Sun, 8 Jul 2001 13:37:26 +0200
=?iso-8859-1?q?V=EDctor=20Romero?= <romero@kde.org>
Re: Pg on SMP half-powered