Subject: Re: e1000 performance issue in 4 simultaneous links

From: "Denys Fedoryshchenko" <[email-masked]>
Date: Sat, 12 Jan 2008 07:13:06 +0200

Sorry. that i interfere in this subject.

Do you recommend CONFIG_IRQBALANCE to be enabled?

If it is enabled - irq's not jumping nonstop over processors. softirqd 
changing this behavior.
If it is disabled, irq's distributed over each processor, and in loaded 
systems it seems harmful. 
I work a little yesterday with server with CONFIG_IRQBALANCE=no, 160kpps load.
It was packetloss-ing, till i set smp_affinity.

Maybe it is useful to put more info in Kconfig, since it is very important 
for performance option.

On Fri, 11 Jan 2008 17:41:09 -0800 (PST), David Miller wrote
> From: Benny Amorsen <benny [email-masked]>
> Date: Fri, 11 Jan 2008 12:09:32  0100
> 
> > David Miller <[email-masked]> writes:
> > 
> > > No IRQ balancing should be done at all for networking device
> > > interrupts, with zero exceptions.  It destroys performance.
> > 
> > Does irqbalanced need to be taught about this?
> 
> The userland one already does.
> 
> It's only the in-kernel IRQ load balancing for these (presumably
> powerpc) platforms that is broken.
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--
Denys Fedoryshchenko
Technical Manager
Virtual ISP S.A.L.