linux-kernel - Re: BFS vs. mainline scheduler benchmarks and measurements

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Date:	Wed, 09 Sep 2009 02:38:37 +0300
From:	Nikos Chantziaras <realnc@...or.de>
To:	Jiri Kosina <jkosina@...e.cz>
CC:	Juergen Beisert <jbe@...gutronix.de>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: BFS vs. mainline scheduler benchmarks and measurements

On 09/09/2009 02:20 AM, Jiri Kosina wrote:
> On Wed, 9 Sep 2009, Nikos Chantziaras wrote:
>
>>>> Here the result:
>>>>
>>>>        http://foss.math.aegean.gr/~realnc/pics/latop2.png
>>>>
>>>> Again: this is on an Intel Core 2 Duo CPU.
>>>
>>> Just an idea: Maybe some system management code hits you?
>>
>> I'm not sure what is meant with "system management code."
>
> System management interrupt happens when firmware/BIOS/HW-debugger is
> executed in privilege mode so high, that even OS can't do anything about
> that.
>
> It is used in many situations, such as
>
> - memory errors
> - ACPI (mostly fan control)
> - TPM
>
> OS has small to none possibility to influence SMI/SMM. But if this would
> be the cause, you should probably obtain completely different results on
> different hardware configuration (as it is likely to have completely
> different SMM behavior).

Wouldn't that mean that a BFS-patched kernel would suffer from this too?

In any case, of the above, only fan control is active, and I've run with 
it disabled on occasion (hot summer days, I wanted to just keep it max 
with no fan control) with no change.  As far as I can tell, the Asus P5E 
doesn't have a TPM (the "Deluxe" and "VM" models seem to have one.)  As 
for memory errors, I use unbuffered non-ECC RAM which passes a 
memtest86+ cycle cleanly (well, at least the last time I ran it through 
one, a few months ago.)
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