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Date:      Tue, 29 Sep 2009 21:03:59 +0200
From:      "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de>
To:        Andrew Kuriger <a.kuriger@liquidphlux.com>
Cc:        Dieter <freebsd@sopwith.solgatos.com>, freebsd-performance@freebsd.org
Subject:   Re: FreeBSD vs Ubuntu - Discuss...
Message-ID:  <4AC25A1F.9000405@mail.zedat.fu-berlin.de>
In-Reply-To: <689d500ec8c95542a53440b8a23ae773@mail.liquidphlux.com>
References:  <200909290226.CAA28246@sopwith.solgatos.com> <689d500ec8c95542a53440b8a23ae773@mail.liquidphlux.com>

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Andrew Kuriger wrote:
> On Mon, 28 Sep 2009 19:26:34 PDT, Dieter <freebsd@sopwith.solgatos.com>
> wrote:
>> In message <cone.1254181613.595484.57677.1000@zoraida.natserv.net>,
>> Francisco Reyes writes:
>>> Steven Hartland writes:
>>>
>>>> Just noticed the following posted on phoronix:
>>>>
> http://www.phoronix.com/scan.php?page=article&item=freebsd8_ubuntu910&num=1
>>>> Comments?
>>> This was discussed in detail in slashdot.. starting with the fact that
>>> most
>>> likely debug switches were not turned off for FreeBSD.
>> "All of the FreeBSD and Ubuntu options were left at their defaults."
>>
>> My question is why is FreeBSD's disk i/o performance so bad?
>> Not just in the benchmarks with debugging on, but in real world usage
>> where it actually matters.
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> 
> Well for one if we look at /usr/src/UPDATING
> 
> "NOTE TO PEOPLE WHO THINK THAT FreeBSD 8.x IS SLOW:
> FreeBSD 8.x has many debugging features turned on, in both the kernel and
> userland. These features attempt to detect incorrect use of system
> primitives, and encourage loud failure through extra sanity checking and
> fail stop semantics. They also substantially impact system performance. If
> you want to do performance measurement, benchmarking, and optimization,
> you'll want to turn them off. This includes various WITNESS- related kernel
> options, INVARIANTS, malloc debugging flags in userland, and various
> verbose features in the kernel. Many developers choose to disable these
> features on build machines to maximize performance. (To disable malloc
> debugging, run ln -s aj /etc/malloc.conf.)"
> 
> Since the article says that they left the debugging features on I think
> this has a bit to do with it. Obviously the testers didn't care to read the
> documentation, and didn't seem to care to use the same compiler which is
> available in ports, I believe it is safe to chuck this lame benchmark.
> 
> ~Andrew
> 

I doubt that debugging switches left in some places a normal admin or
user can't get so easy are the reason why FreeBSD 8.0-RC performs that
bad compared to Ubuntu 9,1-Linux.
The question at this point would be, whether debugging was enabled on
Linux as well or not ...

Oliver



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