linux-kernel - Re: [PATCH] cpu-freq: add troubleshooting section for FSB changes

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Message-Id: <200911072347.05786.trenn@suse.de>
Date:	Sat, 7 Nov 2009 23:47:04 +0100
From:	Thomas Renninger <trenn@...e.de>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	"Luis R. Rodriguez" <lrodriguez@...eros.com>, davej@...hat.com,
	cpufreq@...r.kernel.org, linux-kernel@...r.kernel.org,
	mcgrof@...il.com, Matthew Garrett <mjg@...hat.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Aeolus Yang <Aeolus.Yang@...eros.com>,
	Amod Bodas <Amod.Bodas@...eros.com>,
	David Quan <David.Quan@...eros.com>,
	Kishore Jotwani <Kishore.Jotwani@...eros.com>
Subject: Re: [PATCH] cpu-freq: add troubleshooting section for FSB changes

On Saturday 07 November 2009 11:28:12 pm Arjan van de Ven wrote:
> Thomas Renninger wrote:
>
> > On Friday 06 November 2009 09:01:00 pm Luis R. Rodriguez wrote:
> >> With cpu frequency scaling you may run into some system
> >> performance issues when the FSB changes speed due to the
> >> throughput constraints this brings on the system.
> >
> > Interesting.
> > Could you be a bit more detailed how and what kind of perfomance issues
> > are seen, please.
> > I expect IO based issues like WLAN package throughput or even lost
> > connections :)
>
> the bus doesn't get THAT slow.....
I expected wireless problems because 5 people with @atheros.com are in CC.
There is zero information about the problem itself and possibly affected 
devices/machines.
> in addition, most FSB systems have the memory controller in the chipset,
> next to the PCI logic... so that the FSB bus for DMA transactions only
> carries the snoop traffic, not the whole data.
So when should people look at this?

    Thomas
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