linux-kernel - Re: prioritize PCI traffic ?

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Message-Id: <1168869630.15294.44.camel@localhost>
Date:	Mon, 15 Jan 2007 15:00:30 +0100
From:	Soeren Sonnenburg <kernel@....de>
To:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: prioritize PCI traffic ?

On Mon, 2007-01-15 at 19:23 +0530, Vaidyanathan Srinivasan wrote:
> Soeren Sonnenburg wrote:
> > Dear all,
> > 
> > is it possible to explicitly tell the kernel to prioritize PCI traffic
> > for a number of cards in pci slots x,y,z ?
> > 
> > I am asking as severe ide traffic causes lost frames when watching TV
> > using 2 DVB cards + vdr... This is simply due to the fact that the PCI
> > bus is saturated...
> 
> How do you know that the bus is saturated?

I simply dd if=/dev/sd? of=/dev/null from four brand new sata-harddisks.

> Are you streaming data to/from the ide hard disks/CDROM?

yes.

> Do you have DMAs 'ON' for the hard disks?

yes.

> Is everything just fine if there are no IDE traffic?

yes.

> Are you running 2.6 kernel with preempt 'ON'?

no: CONFIG_PREEMPT_NONE=y

> Are all hardware on the same IRQ line? (shared interrupts)

no: libata devices are on IRQ 16 and DVB devices on IRQ 20

> > So, is any prioritizing of the PCI bus possible ?
> 
> The drivers + application indirectly can control priority on the
> bus.  Just reduce the priority of the application that uses IDE and
> see if adjusting nice values of applications can change the scenario.

That unfortunately did not help... no change...

Soeren
-- 
Sometimes, there's a moment as you're waking, when you become aware of
the real world around you, but you're still dreaming.
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