shared irqs and performance
sandy at krvarr.bc.ca
Tue Sep 14 22:32:31 PDT 2004
>>>>> On Wed, 15 Sep 2004 10:21:52 +0530,
>>>>> Subhro <subhro.kar at gmail.com> said:
> The card won't be facing any stability problems. And there is no
> reason why you should force the card to another IRQ because modern
> motherboards DOES allow IRQ sharing and there is no performance hits
> for it.
That's supposed to be the case and is usually the case. However, when
left to its own devices, my Supermicro P6DBE board would always share
an IRQ between a triple channel Mylex extremeRAID 1100 controller and
one of the channels of a dual channel ZX348 ethernet card. When this
happened, I would always see about 20% dropped packets on the ethernet
channel sharing the IRQ. Manually overriding the IRQ assignment so
that the RAID controller didn't share an IRQ with anything solved the
None-the-less, if there is no obvious evidence of odd behaviour, IRQ
sharing is perfectly fine. However, if things are clearly not
performing as they should, investigating potential IRQ sharing
problems is not a bad idea.
> On Tue, 14 Sep 2004 18:56:18 -0600, Gary Aitken <garya at dreamchaser.org> wrote:
>> On my 4.10 system, I added in a third ethernet device.
>> However, I see from dmesg that the irq assigned is shared with my
>> scsi controller:
>> de1: <Digital 21041 Ethernet> port 0xf880-0xf8ff mem
>> 0xfdfffc00-0xfdfffc7f irq 9 at device 16.0 on pci0
>> bt0: <Buslogic Multi-Master SCSI Host Adapter> port 0xfcec-0xfcef
>> irq 9 at device 17.0 on pci0
>> Since the driver was already present, things went ok, in the sense
>> that the system booted and scsi devices still work.
>> 1. Will this work reliably (I haven't actually hooked anything
>> to the new network card yet)?
>> 2. Even if it does work, I assume it would be better to force
>> it to an unused irq for performance reasons?
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> Subhro Sankha Kar
> School of Information Technology
> Block AQ-13/1 Sector V
> ZIP 700091
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