netdev - Re: Network card IRQ balancing with Intel 5000 series chipsets

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Message-Id: <1167229879.3807.24.camel@localhost>
Date:	Wed, 27 Dec 2006 09:31:19 -0500
From:	jamal <hadi@...erus.ca>
To:	Robert Iakobashvili <coroberti@...il.com>
Cc:	Arjan van de Ven <arjan@...radead.org>, netdev@...r.kernel.org
Subject: Re: Network card IRQ balancing with Intel 5000 series chipsets

On Wed, 2006-27-12 at 09:09 +0200, Robert Iakobashvili wrote:

> 
> My scenario is treatment of RTP packets in kernel space with a single network
> card (both Rx and Tx). The default of the Intel 5000 series chipset is
> affinity of each
> network card to a certain CPU. Currently, neither with irqbalance nor
> with kernel
> irq-balancing (MSI and io-apic attempted) I do not find a way to
> balance that irq.

In the near future, when the NIC vendors wake up[1] because CPU vendors
- including big bad Intel -  are going to be putting out a large number
of hardware threads, you should be able to do more clever things with
such a setup. At the moment, just tie it to a single CPU and have your
other processes that are related running/bound on the other cores so you
can utilize them. OTOH, you say you are only using 30% of the one CPU,
so it may not be a big deal to tie your single nic to on cpu.

cheers,
jamal

[1] If you are able to change the NIC in your setup try looking at
netiron;  email Leonid.Grossman@...iron.com they have a much clever nic
than the e1000. It has multiple DMA receive rings which are selectable
via a little classifier (example you could have RTP going to CPU0 and
rest going to CPU1). The DMA rings could be tied to different
interupts/MSI and with some little work could be made to appear like
several interfaces.

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